Hi Sully. This really is not an Excel question. It is Windows File Association issue, at least from what I understand.
If I understand correctly, I have seen instances where, when looking at the list of files in Windows Explorer, the small icons associated with files are not the right icons, and the problem is not just Excel files. Excel icons where changed to WinZip icons, Word icons were changed to Powerpoint, etc.
If this is what you are speaking of, again, it is not an excel issue.