programs and requirements:
Xbox 360 hDD transfer cable, (just call microsoft and ask them for it, it took me 2 tries)
Hex editor (Google a hex editor, I use HxD)
A brain and some time.
Xplorer360 (again google is your friend)
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Today, I will try and tell you guys how to modify your gamerscore and add any games to your played games list if you want MORE gamerscore.

First I will say, that you will use this at your own risk, don't blame me if you do something stupid, thanks.

Step One: Play ANY GAME offline, in my case, I'll play lets say, NBA 2k10 Draft Combine, now you don't have to necessarily play the game, but just start it up.

Step two: Turn off the 360 and connect you harddrive to your computer

Step three: Open Xport360 or Xplorer360 and goto Partition 3>Content>Look for your profile>FFF folder> Your profile, and extract your profile to anywhere

Step four: goto this site: Kingla's XBOX 360 HDD Folder List, and search for the game you played offline, so I will look for NBA 2k10 Draft Combine.

Step five: Open up your profile in your hex editor. Click find and search for the game ID of the game you played offline.

Step Six: Now you should see some letters of the game on the right hand side, so it should be like N.B.A..2.k.D.R.A.F.T. etc.
No you replace that value with the game id that you want

step 7: just rehash or regisn and put it back on your 360.

Have fun.

I will be posting pictures soon, so don't panic, and if you have a transfer cable I can try and do this for you guys.