F8 didn't work before, but this morning it worked, I was able to boot into safe mode - and use System Restore. I set it back to October 31 and it worked - it came up properly. I'm going to run chkdsk and then defrag, hopefully it'll be back to normal now. As for Tech Guys, I've bookmarked them and will definitely use them as a resource in the future.
To answer a few questions, there is no 'administrator' account on the desktop, the main account is mine. There are also accounts for my husband and son, and a guest account. I run Trend Micro for antivirus/security, and to tell you the truth, I think there are some conflicts that have developed with it. When I did the system restore it quarantined several Trend Micro files, and when I re-logged into my account once I got it working, Trend Micro needed to do a huge update and a restart. Perhaps they sent out an update that caused this, I don't know. So now, I'm running a cleaner/defrag program I was advised to use on the Windows Secrets newsletter, it's going to clean and optimize the registry, remove temp files and then run a thorough defrag. I've also deleted all cache files from Firefox and compacted my Thunderbird inbox. Hopefully this will bring things back to whatever normal is these days on that computer.