You mentioned formatting and reinstalling XP but if you didn't also install current drivers for the chipset/motherboard, audio device, video device, ethernet card, dial-up modem, etc., then it can easily cause the crashes you have seen.

In addition, you don't mention which service pack you currently have on the machine. If you're not at SP2 or SP3, then you should do so.. The service packs frequently fix such issues. And you've also installed the most recent Windows Updates?

Although the antivirus and antispyware programs you have installed are good enough to do the job, remember, they can only prevent part of the influx of malware.. It's YOU who become the best protector of the computer.. Update all your software, such as Java, etc.. Don't use P2P music downloading software.. Don't open attachments in email unless you know EXACTLY what it is and who it's from.. Don't visit bad websites.. When surfing the internet, don't visit dubious websites and when surfing, harden your browser, whether it be Internet Explorer, Firefox, Opera, or something else, do the research for techniques to make them more secure.

Hope this helps.

Grif