Can't start Windows any more

I had been using Parallels to run Windows on my Mac for a while with no problems. All of a sudden, I am not able to start it up. Here's what happens:

1) Windows looks like it's starting, I see the logo and the bar underneath.
2) An error box pops up, with a red x, no text explaining the error, and an ok button.
3) Whether I hit 'ok' or I just exit the error box, I go to a welcome screen with my username.
4) When I click on the username, it looks for a second like it's going to log in (I see the wallpaper), but then it reverts to the wordless error message and says it's logging off.
5) This brings me back to the welcome screen with my username. No escape from the loop.

Any thoughts on how to resolve this, and whether it sounds like a parallels issue or a windows issue?

Can I reinstall parallels without losing the info on the windows partition?

Thanks

 

It's GOT to be a Windows issue.

A couple things to try:

Once at the welcome screen, try sending ctrl-alt-del to see if you can get the regular login screen - then try getting in as Administrator.

Second, just like on a real PC, start tapping F8 once the POST / BIOS screens flash by - and before it switches to the Windows loading screen. You'll then see the advanced startup screen. Select Safe mode with networking.

Either way, once in, you should be able to start hunting down whatever gave Windows an atomic wedgie.