If you have a legal copy, use (part of MAME tools) to compress it:
The original Guitar Hero II DVD-ROM is reported to have a file size of approximately depending on the format and whether it's been archived in a compressed container like a RAR archive. This is a substantial amount of storage space, which is a key reason players seek out highly compressed versions of the game. Guitar Hero 2 Ps2 Iso Highly Compressed
Depending on how you play, choose the format that fits your setup: CHD (Compressed Hunks of Data): If you have a legal copy, use (part