So...it had been more than a month or so since I did some computer clean up. I ran disk cleanup, and set my checkdisk to run at the next startup. It did that (took almost 2 hours because it found some bad sectors I think) and start up was fine.
The next thing on my list was disk defrag. I am using the built in XP defrag program, but I get the error "the connection to the defragmenter engine has been lost. Restart degragmentation". I get the same error whether I choose analyse or defrag. Restarting the program/computer didn't help.
Since the last defrag I installed AVG free version and Zone Alarm free version. Could either of those caused this?
I did some googling, but I there were a lot of sites that really had no fixes, just suggestions, but I wasn't sure what to try first. A few sites mentioned possible malaware causing it.
I haven't tried running it in safemode, so I don't know if that would help.