Back to normality.
I got my Service Pack 4 disk from Microsoft yesterday. That was quick, I ordered it on Wednesday. So I put the Windows 2000 harddrive back in, ran the de-worming utility, installed service pack 4, installed the patch, and installed Zone Alarm. So now I feel ever so slightly more secure. Everything is running properly so far, but Zone Alarm's prompts are bit disconcering: "Internet Explorer is trying to access the internet! Do you want to allow this?" Sure, why not.