I think the program association is somehow changed for all exe files.
Try the following steps, test the issue after each and let me know the results:1
Use the following link to download a file named exefix_vista.ziphttp://tinyurl.com/2vvtby
If you get any option to Save or Run, select Save
Once downloaded, right click on the file and select Extract All
to extract the contents
Open the folder where it is extracted.
Right click on the file named exefix_vista
and select Merge
Restart computer once2
If the problem remains, use the following linkhttp://www.winhelponline.com/articles/165/1/Restore-the-exe-file-association-in-Windows-Vista-after-incorrectly-associating-it-with-another-application.html
Scroll a little and download the exefix_cu.reg
file present under Attachments
Once downloaded, right click on the file and select Merge.
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Let me know results so that I can follow up further