right i just bought a DC off ebay, and got loads of games, my bro bought a few games like power stone and stuff, but they were backups.

now can the dreamcast be modded? or hacked like the x box was?

I think you need a boot disc or some such thing, no modding involved. I think it also depends on which production version of the DC you have. That's all I know.

For a fact, you do not need to mod a Dreamcast to play a backed up game. Some games require a bootdisc while most are made to be self booting. I do however believe that Sega towards the end of the DC run started producing some Dreamcast's that had a different motherboard that would not allow for botting of a backed up disc.

Side note:
Another myth about Sega and the Dreamcast is that they went under because of game piracy. This is complete bull. 99% of the world does not download pirated copies of anything.