Thank you for telling me that- it found 99 problems. It seemed to fix the problem, at first. But after rebooting three times, it froze again. It only took a second try to get it going, though; instead of the six times it took this morning. So I don't know if it was just a coincidence, or it helped.
Sorry if this doesn't make any sense (I don't know much about this as you can tell) or has nothing to do with anything, but it seems that when there's something else going on during the restart, like when you install a new program and it has to restart, and when it does it says updating configuration (or something), and has that progress bar and stuff, it boots up just fine.
Also, I wonder if one of the start up programs is causing the explorer.exe to stop responding, or if explorer even has anything to do with it.
Well, thank you for your help so far - I really appreciate anything you (or anyone) can do. I'll understand if there isn't anything that can help.