"Upgrade to Win XP will solve all your problems"....
Any version of XP will run like a dog on an old system like this - "..Pentium 3 500Mhz processor and 384mb memory.." - no matter how much memory you have. Don't.
If you're happy with the system and just need more storage space just put in a 40-60GB drive as slave - with this mobo you won't notice much difference between 7200 and 5400 rpm.