I was using a friend’s computer with Windows 7 Ultimate 64bit with IDM installed. Once an EXE was downloaded, I clicked on “Open With” instead of Open and selected an application (WinRAR). Since the downloaded EXE file was a self extracting archive, I just wanted to view the contents using WinRAR. However, I neglected the grayed tick mark in “Always use the selected program to open this kind of file”. After that, every program started opening with WinRAR. Even if you manage to delete the offending program somehow, you will get a “Windows cannot find .exe file. Make sure you typed the name correctly” and the problem will still not be fixed.