Hello Jgran, and welcome to Seven Forums.
It sounds like your assocations got messed up somehow. Downloading and merging the exe
(LNK) options in the tutorial below may be able to fix this. It will restore their default associations.
Default File Type Associations - Restore
Afterwards, I would recommend to use the free Microsoft Standalone System Sweeper
to scan your system for malware to help be safe.
Hope this helps,
I was to slow this morning.