windows no disk error message

I tried to view an email attachment that required quicktime -which I did not have. So I tried to download a free quicktime from apple - this did not work. After that I got an error message/dialog box that said windows no disk - cancel, try again, continue. None of which would work. After this I could not gain access to the internet, and win explorer/my computer did not work. I paniced and tried to do a clean win xp install. This did not work either. Then I hit on the idea of unpluging all USB cables - that worked. After I start there is no error message and so I plug all USB cables back in and can continue working. However, if I shut the machine down and restart (w/all usb still pluged in) the same error message comes back and machine is unuseable until I unplug all usb and restart. I hope there is some solution to this other than having to unplu/replug usb each time I want to use my computer. Please advise.

do you know the quicktime attachment was from a reputable sender? the combination of that and the symptoms you have whispers (virus) to me. Do you have an antivirus, and was it on when you opened the attachment?

epheme, I do know the sender. I believe I haad antivirus running. I have run an antivirus since then - I will try that again. Thanks for reply