As standard procedure for a PC that was randomly rebooting and generally dogged, I ran the boot-time scan, and only deleted what was obviously crap, and executable. However, I did move some other things to the chest.
Well, now it reboots just before logon (the blank blue comes up after the video driver loads, then it goes). How can I, from another PC (if Avast! is needed, it's there, too), get files out of the chest and back to where they came (note that I don't necessarily know the full path, if they are easy to get out), so as to begin a more manual malware removal process?
If it helps to find the file causing problems in general, too (though slightly OT), there's something with "system" then "logon", in braces, and "error" somewhere in there (since it reboots immediately, I haven't grapsed the whole thing).