Originally Posted by archalien
Technically speaking, the more ram you have the slower it is (on a per lookup basis) because you have a larger "Table of Contents"(not the technical term haha) to search through.
Yet the more ram you have, the more can be stored there, equating to less lookups on the hard drive which are extremely slow compared to a ram lookup.
To rephrase what he said a little:
When you look up data, your processor first checks the cache, which is VERY fast. If the data isn't found there, it checks RAM next. RAM is not as fast as the cache, but much faster than your HD. Large amounts of RAM means you can store more there, so you don't have to check the HD as often. However, if the data being searched for is not in the RAM, it will take marginally longer to realize that and go search for it on the HD. But that should never be a reason to not get more RAM, as having more RAM is almost always better*.
* Unless you're running a 32-bit OS, in which case any RAM over 3gb won't be seen.
The process itself is trivial:
Turn off, unplug and remove battery.
Turn over and place on a soft surface.
Discharge yourself of electricity.
Use a screwdriver to remove the bottom center panel, something like 8 screws. Remember where EACH SCREW goes. There's 3 types of screws used, 2 of which look very similar but are not in fact the same.
Remove the bottom panel, spot the existing RAM, remove it, put in new RAM.
Do the above steps in reverse order to put your computer back together.