give this a try
How To Clear the Cache on the Xbox 360
Written by Jordan
Tuesday, 28 March 2006
The Xbox 360 may be an amazing console, but every now and then it will freeze or suffer from a severe framerate drop. I noticed this while playing The Elder Scrolls IV: Oblivion. Sounds didn't match up during battles, the screen would freeze completely, and opening doors would take up to two minutes. This is caused when the cache files on the Xbox 360 hard drive become fragmented and need cleared. Don't call Microsoft and wait an hour or more for a fix. Just read this VERY simple solution.
To clear the cache of your Xbox 360 Hard Drive do the following:
1) Boot up your Xbox 360 and place a game in the DVD tray.
2) After the Title Screen for the game appears, restart your Xbox 360
3) As the Xbox 360 is restarting hold the A Button on your controller until the Xbox 360 load screen disappears.
That's all there is to it. Now you should notice a much smoother frame rate and your games should operate at the fullest level!
the link to the site is
AltHack.com