Someone sent me this. So in case anyone has this problem later on: ''I had this exact problem, but a simple google search fixed it for me. GMG's install script has an extra / in it, hence the error having two slashes after Arma II - PC. To fix it, you have to edit your registry. If you aren't comfortable doing that, you're kinda screwed, but might give it a try anyway. Be sure to backup your registry before you do ANYTHING in case you mess it up. Once you're ready, find "regedit." You can use the Windows 7 Start Menu search or you can use the run window on any Windows OS. Once the editor is open, navigate to HKEY_LOCAL_MACHINE/SOFTWARE/Wow6432Node/Bohemia Interactive Studio Click once on "ArmA 2" and in the right side of the window, right-click the MAIN entry and Modify... Then, just remove the last \ on the end of the data, hit OK, and close the registry editor. Problem solved.''