Thanks for all the suggestions. I had the idea that there was a problem due to three things: a new piece of software reported .dll's that were supposedly in the C:\documents and settings\Admin\Local Settings\Temp folder that I did not find when I looked using Explorer - so I thought it might be stealthed .dll's. I ran Ice Sword and did a log and reboot but that program failed to start up after that due to an initialization error, so I was starting to worry. I found nothing with Process Explorer, but a well-stealthed root kit might not show with that. I then ran Rootkit Revealer and found two keys with embedded nulls and a key that Revealer could not access. I booted with a PE disk and looked at the \Temp folder again and saw a .dll file, but with a different name than the ones reported before. I tried using the Regdelnull (Sysinternals) file on the registry and used the remote registry editor to look at the result. Well, the inaccessible key turned out to be a SCSI driver key, with an owner name that was a long string of numbers. I could not delete the key, but I was able to edit the key's values and I renamed the .sys file that it pointed to (no SCSI connections on my system, so I was not worried). The owner string probably refers to a system ID for SCSI devices, but I didn't need to take the chance that it was dangerous, so I nuked it. Turns out the file was harmless according to Virustotal's scan. The keys with embedded nulls are apparently legitimate??!!! If you see a Rootkit Revealer report that shows:
as keys with embedded nulls, they are probably not a problem (although a rootkit that used those keys would be a real problem, because Regdelnulls doesn't touch it). After a few more checks, I think that it was a false alarm, But I was beginning to think that I had an unknown rootkit, especially when I had crash problems with Sysinternals' Autoruns when I referred listed items to Process Explorer. Anyway, thanks again, especially for your suggestion jgpaiva.