Hello tech27, and welcome to Seven Forums.
Do the themes still work when you click on them?
Did you modify those themes at their default
C:\Windows\Resources\Themes folder location?
For now, you might see if downloading and merging the .reg file for the listed theme option in the tutorial below may be able to help. It will restore the default associations for .theme files.
Default File Type Associations - Restore
Hope this helps,

Shawn