to get over 100,000 gamerscore visit
http://tinyurl.com/ykf8wn9
The most I can prove is that I got it in one day but I actually got all 10k in one hour.
I can do this for you no worrys email me

*update*
I can now glitch 50,000+ with 900+ on all games. I would upload a new video but my video card is fried. I can show you my 130,000+ account as proof on request

eligh3121@hotmail.co.uk

I have done this for over 200 people, i can prove it is a legitimate service if you are interested (email me), i used to offer it on ebay, my ebay feedback link is shown below.
@the people saying i changed date:
right b4 u moan saying i set clock back u only get a date linked to your achivs' if you did it whilst connected to live, if you are not connected to live then you do not get a date (im sure you are used to that lol)the date will always be right when connected to live...still wanna moan? i have 2 vids of the achivs actually unlocking. spiderman 1k and pgr 600 or somthing
Heres some games i can do
Gears of war 2 1,000 (Includes seriously :P)
Xmen 1,000
left for dead 1,000
need for speed prostreet 900
stranglehold 700
virtua tennis 3 1,000
Assassins creed 1,000
Crackdown 1250
Full auto 960 ( or 1k if i do some legit)
Virtua Fighter 5 1,000
viva pinatta 900
fifa road to world cup 1,000
Pgr 3 8,70
hexic HD 200
spiderman FOF 1,000
dirt 1,000
hitman blood and money 800
cammand and conquer 975

ebay feedback
http://feedback.ebay.co.uk/ws/eBayISAPI.dll?ViewFeedback2... (less info)