Alright, I wiped the HDDs and reinstalled the OS. Everything's working fine so far, so although we didn't "solve" the issue, per se, since the problem's gone, I think we can mark it solved, chuck it into a cell in the archive, lock the door and throw away the key.
Just before you do that, can you tell me: Does MS Security Essentials function as a firewall, or do I need a 3rd party firewall? BTW- Windows
Firewall?!? More like Windows'
Continent-Sized Bullseye!...On second thought, put the key somewhere a PM can get at it.
Finally- Go raibh míle míle maith agat (a million thanks) for all the effort you put into trying to fix my computer, even if it was in vain in the end. ...Well, I doubt the site will let me add a million thanks to your profile, so this will have to serve as the remaining 999,999 thanks.