Ahh you have NTSC as standard... Then you should have no problems playing PAL games in NTSC modes (as your X3 BIOS might set it to then).
NTSC is 60Hz and PAL is 50Hz so NTSC can handle PAL but PAL can't handle NTSC... Not in themselves atleast. Like when I try to play some NTSC games I get bad stuttering (the sound) and in-game movies goes real bad. When I change to NTSC region my TV gets Black&White with no sound (my tv can't handle NTSC).
My TV can however handle PAL 60Hz mode but there is something else that is different too so... No luck for me...
However I am waiting to hear from sharkfin and his GTA: SA as I know there was an AV-fix released for the NTSC version of GTA: SA so it could be played on PAL xbox. But the PAL version is playable directly when moved from the DVD to the HDD. Atleast for me.