Most laptops have two slots for SODIMM (a smaller version of DIMM used in laptops) memory modules. The M6000N's primary internal slot came filled with a 333MHz 256MB DDR module, and its external slot was empty.
Intel's Centrino chipset (855PM) will run memory up to only 333MHz, so even if you use faster, 400MHz modules, the M6000N will run them at the slower speed. Powerful desktop-replacement laptops are more likely to support 400MHz memory.

Accessing the M6000N's external memory slot is easy.

1. Pop off the memory-bay cover, located in the middle bottom of the laptop
2. Pull apart the side clips holding in the current module, and gently pull the module loose and remove it.
3. Insert the new stick at an angle, making sure the notch on the SODIMM's edge connector matches with the key in the memory socket.
4. When the edge connector is fully inserted, press the module down until it snaps into place.
5. Leave the internal slot alone

Accessing the internal slot is easy on the M6000N but can be considerably harder with many laptops. In some cases, it's under the touch pad, and you need to disassemble most of the laptop to reach it. It's an extreme operation that even the most experienced get nervous about. The 855PM chipset doesn't support dual-channel memory architecture, so you wouldn't be losing any speed if you weren't able to access the second slot. But you would give up the opportunity to upgrade to the full 2GB of RAM; the best you could do would be 1.256GB.

To replace the RAM module, release the clips holding it in place and carefully pull it out. Insert the new one at an angle and snap it into place.