See if you can figure this one out.

Hey guys been trying to play custom guitar hero songs for a while now. I have my game already rebuilt to ISO format. It's about 2GB or so. I have:

Fat PS2
Seagate FreeAgent Go! 150GB external HD
USBeXtreme (purchased version)

I formatted the drive per instructions, extracted the ISO off of a DVD I had to burn because there's no option to load it from my desktop (boggle), and hooked up the external to my PS2. It boots to the external, sees Guitar Hero, then after about 6 seconds the screen turns black and I have to reboot. I can move around in the menu screen for about 6 seconds but like I said, it just dies after that. I'm about this close { } to just giving in and buying a premodded ps2. Hopefully you guys are whizzes and can figure this out otherwise I spent $150 for a coaster and a music holder.

Thanks in advance.