Thanks for all the help so far, Bongo!
Desktop Window Manager Sessions Manager is disabled, not running, and the option to start it is greyed out.
sfc \scannow didn't finish, so I ran it at boot using method 1 here:
SFC /SCANNOW : Run in Command Prompt at Boot That gave me the error "There is a system repair pending which requires reboot to complete." I rebooted into windows and then back to the disc several times and got the error each time. My computer does not have a pending.xml file.
Another symptom that is probably related (probably the cause, I think now) is this: when I go to Control Panel\All Control Panel Items\Performance Information and Tools and click "Rate this computer", it crashes before it's done.
I think I'm going to try doing a repair install like here:
Repair Install
What's your opinion on any of this?
EDIT: I ran the compatibility check (by clicking "upgrade" after starting setup) on the windows 7 disk and it gave me this message: "Windows needs to be restarted so necessary changes to system files can be made before continuing."
Restarting, however, does not accomplish this. What can I do?
I started a new thread here because the issue now fits that forum category better: Cannot clear "System repair pending which requires reboot to complete"
Please join up at the other thread if you can still help, please, Bongo. Should I mark this current thread solved, even though it isn't?