I won't be responsible if you mess up something with your computer.
(This guide is not for newbies)
EDIT: UPDATED GUIDE HERE: http://xliveaf.co.cc/
If you are not sure how to do this, or you don't understand some step, watch this video.
1. Download a hexeditor and install it. Example: Hex Workshop
2. Write down the "E0xxxxxxx" code from your savegame folder which ones XLive account you've lost.
3. Create a new XLive account.
4. Go to "C:\Users\<user>\AppData\Local\Microsoft\XLive\Content\E0xxxxxxxxx\FFFE07D1\00010000" (If you can't go to there, turn hidden folders to visible)
5. There you will find a one file, open it with the hexeditor.
6. Find following lines:
7. Now replace the underlined lines with the code you wrote down at step 2.
(Notice the upper line, it is writed backwards)
8. If you can't find the lines, it's the same code that the Xlive account has (shown in the video).
9. Save the file you edited.
10. Rename the following file and folders with the code you wrote down at step 2:
C:\Users\<user>\AppData\Local\Microsoft\XLive\Content\E0xxxxxxxxxx\FFFE07D1\00010000\E0xxxxxx (the file you hexedited)
C:\Users\<user>\AppData\Local\Microsoft\XLive\Content\E0xxxxxxxxxx\FFFE07D1\00010000\E0xxxxxxxxxx_MountPt (leave the "_MountPt" at the end, don't remove it)
10. If your old savegames aren't already in the folder where they should be, copy them to "C:\Users\<user>\AppData\Local\Rockstar Games\GTA IV\savegames"
Edited by -zerox-, 11 May 2010 - 06:34 PM.