I don't see which OS but the .EXE association is blown. Either by virus, trojan or registry cleaners. For most versions of Windows I can fix it with Doug Knox's .EXE association fix.
I'd think over how this happened.
-> Read http://www.dougknox.com/xp/file_assoc.htm *again, almost all versions of Windows uses this fix.
I dont know what have i done to my pc, but when i want to open an application ( ex: google ) the respective app is opened with Windows Photo Viewer.....and this happens to all apps or files ( all of them are changed to ”.exe„ , and I can not do anything to them.