You need a 64 bit OS and a Motherboard/processor that supports the 64 bit architecture. If you are running 32 bit OS like Windows you don't even get use of all the 4GB, it is more like 3.5GB. If you run 64 bit, there is more memory freed up for your programs, so if you have been memory starved and the OS had to put stuff in virtual memory then you will se a big improvement out of even 6 GB. If you are in the habit of keeping many programs running in the background a 64 bit system and at elast 8 GB (more is better) will let you run many programs without slowing down. All of the recent Intel processors support 64 bit operation.