Thanks, guys. To answer some questions, yes, I have a daily updated virus killer and ZoneAlarm firewall, no, I don't open spam, but my local folk-forum habitually use attachments. I don't open any others. The previous HD was installed new when the machine was built two years ago, 30gig. No, I'm not scared of the thing, I've built one (my business 2.6) and replaced parts and now completed six format-and-reinstalls. Full formats. No, it isn't bloated, barely 3gig in the original HD, just operating essentials in it now, yes, I've tried Norton Systemworks, ZoneAlarm System Mechanic, Spybot, two virus killers on it, all with no improvement noticeable. There is little likelihood of lots of porn or anything else on the original HD, as it belonged to my son, who is embarrassed by such things. I simply can't get on the net with that machine, so many diagnostic actions are out. Experts I've used have just replaced parts, at inflated prices and horrendous charge-out rates. I forgot to mention that I use a spike-arrester.
I borrowed a CD set that said it was Linux, but it was an OLD edition.
I hate to throw a good HD away because some troglodyte wants me to.
I'll try Bruce's suggestion first, on this little HD, and fight on from there, as I have to format it anyway, because Windows is missing two files and won't work properly. Thanks again.   Chris