So, I install the game and play for a few hours. After I get out and do other things, say surf the web a while, I go back and double click the vendetta.exe icon and it says "vendetta.exe cannot be found".
Search the C: drive and it is nowhere to be found, though the folder is still there.
I reinstall and it works fine one time then same thing.
I'm on Windows 7 home premium.
Any ideas? I've never encountered anything like this.

Im not completely sure, but it sounds like the icon's path may be messed up? Right click the Icon and goto Properties. Check to make sure the path for the executable is to the right folder.

Hope this helps!