Reset Gamerscore

I'm afraid that there is no way to reset a legitimate gamerscore at all. Gamerscore resets are only given to people who illegitimately modify their gamerscore. When they get their gamerscore reset, however, there are a number
of other consequences:

1) All of the gamerscore will be reset to zero.

2) A person with a gamerscore reset will be permanently branded "Cheater" on your gamertag.

3) All lost gamerscore and achievement are gone forever, and irretrievable.

No one here can.Only the enforcement team can reset gamerscores.

You can't request a gamerscore reset but if your gamerscore is modded it will get reset eventually.

I don't think your friend got to keep any gamerscore from then. Once a reset is done all achievements are lost regardless of how they were gotten. Also, once reset you can never re-earn those achievements again.

I hate to butt in like this but a gamerscore reset resets and locks off all achievements regardless of whether they were earned or hacked. It's supposed to act as a deterant but for some reason people do it anyway then whinge when they're caught and punished.

That's an issue determiined by the Enforcement Team and they all hang out in
http://forums.xbox.com/xbox_forums/xbox_support/f/41.aspx