XP is much more demanding of system hardware than 98 was. Often the problem is the RAM. Take it out and reseat it for sure. I'd try to borrow another stick and try that.
You can get Memtest86 to test your system at a low level. If Memtest displays errors you can expect XP to blue screen, freeze and/or reboot. Once Memtest runs cleanly the blue screens, etc. should be resolved. If not, then a clean install of XP makes sense.
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