HI ^ ^! new here, help needed!

hi~ i jst found out that my xbox is modified...;;;
its 80gb hardrive... so its seems to b waste cuz it has like nothin on it.
seems that i have dvd2xbox app. and i try using it but except
i couldnt find ANY xbox iso's....;;
can anybody help me find good solid websites for xbox iso???
and is it possible to move xbox real game cd's to xbox? so like if i borrow a
game from friend, ( bought cd game) ...can i move it to my hard drive?
or do i have to move the file from the bought game and burn that to dvd?