Well I got a system that runs on XP 128 SDRAM and never had such crashups ok but Trend Micro Pc cillin 2000 had some problems.Do these in order
1.Boot Up In Safa Mode
2.Get Rid Of Your Current Antivvirus
3.Get Norton Av 2004
4.Get The latest Updates form Other Pc/Internet(dont connect yours, you will have a pool of virus without av on ur pc)
5.Boot in normal mode
6.Press Ctrl+alt+del and see which process is consuming more memory ,end task for that
7.Start the scan

If still problem persists contact The Forum -post a message we will be there.
Note: The problem might be also for Ram but my Pc runs fine
config
p4 1.5ghz
128 SDRAM
40 Gb Hdd
Ge force 2 mx Agp(64Mb Mem)
And
Kobian p4m266 NDFX Mtherboard
Thank You