The following are the steps to complete before, during and after removing the hard drive from an old system and install it a new computer.
Transferring an old hard drive to your new computer can be a really good idea, for a number of reasons. First, it makes certain that none of your confidential data--credit card numbers, passwords--winds up in a garage sale, and eventually in the hands of a hacker.
Secondly, it gives you two physically separate hard drives in the machine, which you can use as a quick and simple backup solution. Just copy your important files from one drive to the other, and you're now guaranteed that even if one drive has problems, your backed-up data will still exist on the other drive. You can obtain inexpensive backup software that will automate this task.
Finally, using your old hard drive gives you extra storage space for free!

The transfer should be done on a slave basis only.
Attempting to use your old drive, especially with XP, as the primary boot source can easily cause an OS ''transplant'' shock. Upon the first-boot registry loading, Windows discovers a different set of hardware has replaced its familiar legacy setup for which there may or may not be compatibility with Window's existing CurrentControl/Services layout. This could cause a Hardware Abstraction Layer breech and the result would be a failed boot-up. There is one more issue here; one for which most do-it-yourselfers are into complete denial! And that is OEM copyright violations. Without going into detail here, transferring an old primary Dell drive, say, into a new HP, to be used as its primary boot drive is breaking the law!
Microsoft is and has been fully aware of this practice for some time and has incorporated special OEM manufacturer-use copyright protection features into it's newer operating systems. An XP system modified for Dell knows right away that a bogus implementation attempt has occurred when it's system-embeded copyright modules discover the HP hardware signatures.

You can, however, do a transfer without problems on custom build computers. That's because there is no copyright protections on generic motherboard and hardware build-ups; thus, the new signatures are not examined by the old custom primary drive's OS as to copyright validity.
Again, your old drive should be transferred to the new computer as a slave only unless you're using custom build.

Frequently, people upgrade their new machines because the old one stopped working properly; however, the reason it stopped working properly was often due to an unsuspected virus infection. Viruses live on the hard drive; and if you transfer the old, virus infested hard drive to the new computer, you'll infect your new machine as well. Fortunately, there's an easy way to protect yourself. Your new computer probably came with a virus protection program already installed; make sure it's working properly, then visit the manufacturer's website and update everything. In particular, make certain that the virus definitions are right up to date.
A good antivirus program running on your new computer will detect and eliminate viruses on your old hard drive automatically. But that program must be there, and be working properly, and be up to date. If it isn't, you could easily wind up infecting your new machine with viruses.

First, open up your old machine and physically identify the old hard drive. Shut the machine off, pull the power plug out of the back of the old computer, and remove the computer access panel or cover.
You're looking for a thin metal box, about 4 inches by 6 inches, and about an inch thick. That box is your hard disk drive. There will be a ribbon cable attached to the back of the drive, which connects to the motherboard; and there will also be a 4 pin power plug, also connected to the back of the drive, which runs up to the power supply. The 4 pin power cable is polarised, so it will only connect one way. The data cable - the ribbon cable - is sometimes polarised, and sometimes not. This means that it IS possible to connect it backwards. However, take a close look at the data cable. It will have a thin red line along one edge of the cable. Make note of which edge of the socket the red line on the cable is aligned with, and connect it to your new machine the same way.

Having made careful note of how the cable is connected, remove the power and data cables - they can be stiff, but they just pull straight out - disconnect the hard drive from the old computer and remove it.
Traditionally, hard drives have used a ribbon data cable, about 2 inches wide, to connect to the motherboard; this was known as a PATA cable, for Parallel ATA cable. This method is going away, in favour of a new type of cable and electrical topology known as SATA, which stands for Serial ATA.

The problem is that SATA is new, and the fine details of how it works still vary from motherboard to motherboard; hence, on some motherboards it is possible to have a mix of SATA and PATA drives controlled by the same primary controller, and on others it is not. For that reason, the suggestion is to install the old PATA hard drive on the secondary controller, along with one optical drive. However, if your new computer already has two optical drives, then you cannot do that. In this case, it will be necessary to connect your old drive - in some fashion - to the primary controller. Depending on your motherboard, this may, or may not, be possible. You'll need to read the manual that came with the motherboard, and probably make some settings changes in the BIOS as well.
However, all of this only applies if your old hard drive is a PATA drive, and your new computer has a SATA drive. If your new computer is still using the older PATA technology - surprising, but possible - then just connect your old hard drive as a slave device on the primary controller.

When the IDE (Independent Drive Electronics) specification was finalised in the early 1990s, it was decided that each manufacturer would handle his own drive data storage method internally, and supply a standard data signal to the motherboard. Further, it was decided that the drive controller - the chip that controls the flow of data from the drive to the motherboard - would control a maximum of two drives, and each drive would be referred to as either a Master or a Slave.
As time went on and CD drives made their appearance, it was discovered that people needed more than two drives; and so it became customary for motherboard manufacturers to include two drive controller chips, which were then labelled primary and secondary. As a result, virtually all motherboards manufactured today have two drive controllers; and each drive controller is capable of controlling two drives. Hence, motherboards today can typically control a maximum of 4 IDE devices. These devices are identified as Primary Master, Primary Slave, Secondary Master, and Secondary Slave.

Your new machine will probably be using SATA technology on the primary side, and the older PATA technology on the secondary side. So you'll be connecting your older PATA drive to the secondary controller. However, the secondary controller will probably already have one device on it; an optical drive, such as a CD ROM or a DVD burner. This device will already be set as a Master device; but your old hard drive will likely also be set as a Master device, as well. The thing you must avoid is having two drives on the same controller jumpered the same way, i.e., two masters or two slaves on the same cable; so you'll need to change either the optical drive or your old hard drive to a slave device. Here's how to do it:

1. On the broad, flat top of your old hard drive you'll see a bunch of printing, and hopefully, a diagram. On the diagram you'll see M or MA (for master) S or SL (for slave) and C or CS (for Cable Select). Cable Select allows the physical position of the drive on the cable to determine if it will be seen by the computer as a master or a slave drive. Dell uses this topology, but hardly anyone else does; so unless your machine is a Dell, you probably won't have to worry about it. Instead, look at the diagram and note the jumper position associated with the SL. That's how you're going to be jumpering the drive.
2. On the back of the drive, where the cable plugs in, you'll see a tiny array of 7 or 8 gold pins, with a black jumper (called a Berg connector) connected to one or two of those pins. This is the jumper array, which determines if your drive will be seen by the computer as a master, a slave, or a cable select drive. It's very likely that your old drive will be set to the 'master' position; refer to the picture printed on top of the drive and get yourself oriented. Now, remove that black jumper and position it over the set of pins marked 'slave' on the diagram. The old hard is now re-jumpered as a slave device.

At this point, you should have one device jumpered as a master, and the other jumpered as a slave. Now, you need to physically mount the old hard drive in the new case. Hopefully, there's an empty bay, but on some cheap new machines there isn't, and you'll have to improvise. If you haven't already done so, shut down your new machine normally; then physically remove the power plug from the back of the computer chassis. Now, with the power disconnected, attach the drive.

Once the drive is mounted securely, you'll need to connect a data cable to the drive. To do this, identify the optical drive on the machine, and find the ribbon cable coming out of the back. Follow it down to the motherboard with your fingers. On the way, you'll find a socket spliced into the ribbon cable; this is the socket you want to plug into the back of your old hard drive. If the ribbon cable going from the back of the CD drive to the motherboard doesn't have a socket on it - very common on cheaper machines - you'll need to replace the ribbon cable with one that will accommodate two drives.
Hook it up the same way in the new machine, with the red mark on the cable on the same side of the hard drive. If you've forgotten, the most common - but not universal - way of connecting a cable to the hard drive is with the red mark on the cable closest to the centre of the drive, and furthest from the outside edge.

The last thing you'll need to do is plug a spare power cable into the back of the old hard drive. This is a 4 pin polarised plug, and it's impossible to plug it in the wrong way. The colour coding on the wires is red, two blacks, and a yellow wire. Typically, there will be some spares coming out of the power supply; find one, and hook it up. In the unlikely event that you have no spares, you can get a splitter or Y cable adapter at most computer stores.

At this point you've re-jumpered your old hard drive so that it's a slave drive, you've physically mounted it in your new machine, you've connected the ribbon data cable and you've plugged in the 4 pin power cord. Now, plug your new machine in and turn it on. Watch the screen; you should see the original hard drive in the new machine listed, followed by a space, followed by the optical device and the hard drive from your old computer.

. Leave the cover off of the new computer (you may need to get at the drive again if there are any problems) and fire it up. Hold down the F2 key on your keyboard as it starts, or whatever key is correct to enter 'Setup' a.k.a. the BIOS settings for your computer - common keystrokes used to enter System Setup are F1, F2 or Delete.
When the Setup screen appears, use the down arrow key to move down the list of settings till you get to the one for the secondary hard drive. When the drive's setting is highlighted, hit the ENTER key, then use the left or right arrow key to change the setting to AUTO. If it's already set for AUTO, leave it alone. Hit the ESC key, and accept the changes when asked if you've had to make any.

Let the machine boot into windows, left click on my computer, and check the drive listings. You should see two hard disk drives; one will be the old drive from your old computer. If you don't,

1. Right click on 'my computer' and select 'manage' from the drop down menu. This will start the computer management console.
2. On the left hand side, select 'disk management'; this will list all the drives found on your machine. If the drive from your old machine is not listed, it means you've got a basic configuration error; the parallel cable is backwards, or the drive is jumpered incorrectly, or the drive is not getting power.
3. If it is listed, there will typically be an error message that will give you a hint as to the problem that windows is having. But typically, with most older drives, you won't need to venture into the management console; it usually is only an issue when you install a drive larger than 127 gigabytes, or thereabouts.

It's possible when moving hard drives (2, dual boot) from a fairly new custom built computer to a new custom built computer (Windows XP), that you may have to a repair install of the OS before it will work.
That's quite simple as you go for 'Instal' on the first screen that comes up, then 'Repair' on the second screen, which also allows you to choose where you want to install if you have more than one hard drive and/or have your drive/drives partitioned.

The hard drive speeds are independent of each other. Both rotational and access time.
A drive designed to run at 7200 RPM cannot run at 5400 RPM at all, without replacing the PCB with one that has a 5400 RPM controller. The motor controller determines the drive rotation speed, and that is fixed by design.

The access time can actually vary pretty dramatically in any given disk drive. It depends on how many tracks you're seeking across, and it varies by where you're seeking from and to... Many drives will have better seek performance seeking from outer tracks towards inner tracks, for example.

Additionally, the performance of the servo system will vary in a drive. A lot of drives will have more overshoot problems seeking in one direction than the opposite direction, for example.
That is why access times are always reported as averages. The PC requests the information and then waits until it is processed by the drive. If your drive is badly fragmented, that can take much longer for some requests than others. There is no problem mixing a high performance, high rpm, low access time drive with a slower drive. The faster drive will perform faster than the slower drive, that's all.