Well it's an iso file on the PC, so I shouldn't be able to de compress it any more... And what is a bad dump? (I'm using sd card)
A compressed iso is an iso that has been trimmed/compressed with a program (like discEX). It saves room on your storage device but causes problems for some games
A bad dump is an iso that didn't get fulled ripped when the person was dumping it
Also try the other (NTSC or PAL) and see if that one works