thanks nihil for a moment I thought people were saying my XP system would be sluggish due to the 2GB of ram I have in there. lol
What types of applications do you run? if you run mainly Video games, internet apps etc then 512 should be good for you. If you run intense apps, such as photoshop, bryce, SQL databases etc then the more memory the better.
Many people in hopes of making their system super fast order a computer with tons of ram, but because they spent so much on ram, go cheaper on the rest of the computer i.e. 5400 RPM HD, 233mhz XP processory, etc. Even though they may have fast ram the rest of the computer slows down the ram thus cancelling out the fast ram .lol
In order to have a all arround decent system its best to try to even everything up. Usually the biggest bottleneck in systems is the hard drives. if you can get a 7200RMP/ SATA/ SCSI / Raptor drive plus some fast ram then you woud see a bigger preformace increase.
Basically what RAM does, is its a place for the computer to store applications currently being used. The less ram, the less space for for current apps to be stored which then forces windows to use swap space (virtual Ram on your HD).
In order for your ram to have the programs put into memory, your Hard Drive must put them there hence why I said the HD is usually the biggest bottleneck. The faster the HD the faster the apps get into memory.
So the moral of this reply is more ram is nice, but if you want true preformacne, about 512MB of DDR ram, and a 7200RPM HD or greater would work out nicely. Preferrabbly if you can afford it, get one of those Western Digital Raptor drivers @ 10,000 RPM's :D lol