cd-xa mode 2 are the settings for burning your backups from images on the hdd, as for why they're not working, well...
1.which mod chip are you using?
2.what boot method?
3.what kind of media cd-r or dvd-r?
4.are your games patched (if necessary)?
5.if cd based games, were they backed-up correctly?
6.if dvd based games, were they ripped or backed-up correctly?
for information on backing up your ps2 games check:
http://www.megagames.com/ps2/ps2_utils.shtml
for patches check:
http://www.megagames.com/ps2/ps2_patches.shtml