Well, it appears that I have several nasty viruses lurking on my computer. I updated my Norton (which I do twice a week anyways), updated Ad-aware 6.0, and restarted the computer in Safe Mode. I ran both programs, and Norton found 33 instances of a Trojan. (Incidently, the Norton site was not very helpful in helping me get rid of the virus. I've tried everything, including digging through the Registry file.) Nothing. It keeps coming back.
*sigh* It looks like I might have to format my hard drive - AGAIN. I had some major problems back in February that necessitated a formatting (it turns out the problem was with the modem, not the system. But it was good to get rid of the superfluous crap.) The big difference is that this time, my computer isn't the hub of a network, and I have high-speed Internet access, whereas before I only had dial-up. Oh, the many joys of high-speed Internet!
Fortunately, I have tomorrow afternoon off (unless someone tells me to stay), so I'll back up the My Documents folder, my Music folder, my bookmarks, and my address book. Oh, and the folder where I keep my downloaded programs. Or at least make a note of which ones will need to be re-downloaded - Firefox and Thunderbird will definitely be backed up so I won't have to start off with IE.