Essentially, using this hack will allow you to store your Xbox saves on your PSP. Please take caution that any current PSP saves will be lost - so create a backup before continuing!

Procedure:
-Obtain a USB adapter for the Xbox controller - any one should do.
-Fire up your Xbox, and go to the Memory area on the dashboard.
-Connect the PSP USB cable to your Xbox USB controller adaptor.
-Put the PSP in USB mode. Wait for the Xbox to detect it.
Select "Erase".
-Copy any saved Xbox games to your PSP and vola!

NOTE:You'll need to reformat your memory stick for re-use in the PSP once you're done.