Halo 2 PAL is 4,49 GB in his total size... that is too big to fit on a DVD5 even after deleting dashupdate.xbe (54MB)..
So the only method to fit it is to delete the Attract Mode (the one that starts when you leave the game running for a long time, without touching any button on the pad, in the initial screen) and substitute it with a smaller file..
So after ripping the DVD on your PC, enter in the "bink" folder and delete the file "attract_60.bik" that is 130 MB ca. and substitute it with the file attached in this post.. (it is a zip file, so first unzip it!!!)
ENJOY!!