Fallout 3 Message Board  

I'm thinking he means the Fallout3.exe.cat file. If you have extensions showing, you'll find it. Also, if you do in fact rename the file, that just means your Windows Live won't log in. It may look like your save file is gone... it isn't... all you have to do is move it from your profile folder (Documents\My Games\Fallout3\Saves\profile name) to just inside the root of the "Saves" folder.

Hope this helps.

[Edited by CJDJ, 1/13/2009 9:05:25 PM]