Before you jump on the band wagon and get 4 Gig's of of ram you need to look at your system OS. A 32 bit OS can only address a total of 4 Gig's this includes video memory, system memory and ram. If your graphics card /cards has a lot of memory installed on them then you may not be able to use 4 Gigs.

Example two 8800GTX = 1.5 Gig of memory addresses required, subtracted from the 4 gig total = 2.5 gig's worth of addresses remaining Installing more than 2.5 Gig's of memory in this system would be a waste of money.

As a general rule of thumb installing more then 3 Gig's in a 32bit OS is a waste of money