Hi all,
Should probably have posted this a bit sooner, but I discovered the problem. It was the Win32.Parite virus, for some reason Norton AntiVirus 2002 wasn't picking it up.
This virus attacks .exe files, and prevents them from working properly, but it takes time for some .exe files to be infected. I had burned some infected files onto CD and was using them when after reformatting, so the problem kept re-occuring.
To fix it, I downloaded and installed Grisoft Anti-Virus Guard, free from
www.grisoft.com. It found about 500 infected files, surprising that anything could work after that!
I found that the best thing to do was reformat again, then install AVG before anything else. Unfortunately I had to download all my setup files again, including Win2000 SP3, over a 56k modem.
Hope that helps.
Scottly