I corrupted XPS files by trying to open with Acrobat - how can I fix?

I am running Win 7 Home Premium (64 bit) on a Dell n5010

I mistakenly thought XPS Viewer was a pdf application. I have a ton of XPS files on my laptop. I recently installed Adobe Acrobat Pro and thought --- stupidly --- that I should make all these files open with the same program, never realizing that XPS is not a pdf reader. You'd think I would have taken the hint when I did "open with" and Acrobat wasn't one of the choices, but I didn't.

So this is what I did to an XPS file -
[a] right clicked, selected Open With
[b] browsed through the hard drive until I found the Acrobat application
[c] finished the process and, in doing so, corrupted every XPS file on my laptop (more than 15,000).

Now, everything that was file type "XPS Document" is now file type "DOWNLOADING file." Most of them now end with .pdf.downloading

I thought that, logically, I should be able to undo my mess by right-clicking, selecting Open With and finding the XPS Application. I the name of the file - thanks to your site - and from there was able to find it on my hard drive. I tried what I thought would be the fix and it didn't.

Is there anything I can do to fix this mess?

Just tried it. I got a message that says:

"Not all data was successfully written to the registry. Some keys are open by the system or other processes."

I tried rebooting, thinking if something was open it would close with a reboot. No joy. Still get the same message.

Advice?

It went through in safe mode but it didn't change any of the files, they still all read *.pdf.downloading. I tried changing the extensions on some of them and it didn't help. Should I post the problem to Associations?

Hey, have you tried to manually change the file extension and the file association?

If not, I suggest you paste this control /name Microsoft.DefaultPrograms on the RUN box, hit the Set Associations link, check the default program for .xps and change it if it is not the Microsoft XPS Viewer.

After that, you change the file extension from "pdf.downloading" to ".xps" i don't know if there is a way for doing this on all the affected files at once.

The file association is set right and I tried to manually change the extension a couple different ways. I just keep getting the same error messages.

What a mess I made.

I'm hoping at this point that I will hear from CrashPlan tomorrow or Tuesday with a solution. I think the old files should still be on their backup, because the ones I corrupted will have new names so I don't think the old files would have been overwritten. I have a new computer arriving on Tuesday so maybe I'll just be able to restore from CrashPlan to the new machine and not have to keep pulling my (and your) hair out over this.

yeah, I did. It didn't help.