Microsoft originally designed Windows to operate on computers that were built with WAY TOO LITTLE actuall RAM. Many companies put way too little ram in their PC's to get them out the door at discount prices, knowing that the Pagefile would pick up the slack, at a significant hit on performance.
When a program can't fully load into the available ram, Windows will shuffle it off to the Pagefile on the hard drive. That's called "Virtual Memory". The real problem with that is that the hard drive is the slowest part of your computer. It's thousands of times slower than the Ram itself.
So the overall solution to the problem is to give your OS enough ram in the first place. For any version of XP, you should try to get up to 2 gig's of ram. Then use of the hard drive and the Pagefile will go down and system performance will increase. I try to do this for all my customers, with OLD PC's, Windows XP and limited amounts of RAM.
Memory optimizers just mask the problem, they don't FIX anything. Those programs actually use up ram when they are running.
You're better off, to either add more ram to your computer, or minimize the TSR's and Services running in the background on your PC.
I do this stuff for a living and have for many years, so I know it's possible.
Good Luck,
Shadow
