-Try a different set of drivers. Any of the 7x.xx ones.. prfrebly 76.44, 78.xx etc. Check if things are smoother.
- Are the two of you having same resolutions..? (or he is gettin better fps on a lower res.)
- Borrow his ram-sticks ( 2 of 'em) and try on yur system. if things look smoother, you knw whats wrong
and what PSU/smps do you have? whats the +12v rating on it?