The contradiction is: "any kind of file" (including text-files, mp3-files, Word documents) versus "exe-files (only)".

Assuming it's only exe-files it's likely you have some malware on your system. Read Grif Thomas' post

First apply the registry patch he mentions to get the exe's running again, then run all the scans.

Do you have any indication how your machine got infected? What protection measures have you taken?

Hope this helps.