I did the clean install from upgrade months ago, and it has all worked very well.
Yesterday, using MSE, I got a 'severe threat' warning. I think I told MSE to clean the computer, and it showed after I clicked on that button that no threat now existed. Maybe that was my mistake. I know one of the other buttons was 'take recommended actions' or something like that.
Regardless, it all worked fine, and I shut it clear down. Today it hung on startup and wouldn't get to the logon window.
I don't have a system image.
I booted from the Windows 7 disk and initiated 'Startup Repair'. It has been "searching for problems" for 30 minutes now.
Just getting to the Startup Repair took a long time.
This is on an HP laptop with plenty of memory and disk space.
I do have system restore points and have not tried them, went straight to Startup Repair.