Thanks, I'll give it a try. I hope I can get XP to boot up again. I'm in it right now after about a dozen tries. I looked at ntbtlog.txt in Windows and there are some drivers problems alright. It listed about 17 drivers that loaded, and then started listing lots and lots of drivers that didn't load......repeating some or all of them. I just happened to have bought another Mouse of the same type, Microsoft Wheel Mouse Optical USB, so I have a disk with current drivers on it.
Addendum:
I uninstalled the Mouse drivers and rebooted. I got a message to update part of the motherboard bios so I updated it all. It wasn't really an update, just a replacement of an earlier update that I downloaded several months ago. After that I rebooted again and put in the disk from a brand-new mouse of the same variety, and I got a message that the driver couldn't be updated because a more advanced driver was already installed. Since then I have turned off the computer two times and booted up again with no problems. I haven't checked a new bootlog, and probably won't unless I have more problems. Thanks again. My fingers are crossed.
Addendum:
The issue is resolved. Thanks again.