Got a new 12'' PowerBook with 40GB 4200RPM HD. I am thinking about swap it with larger and faster HD. I have seen some Hitachi 7200RPM HD that claims is compatible with new PB line. Anyone has done this before? Is it really hard? BTW, does 7200RPM sucks a lot of more battery juice than 4200RPM HD? Any suggestion or advices would help! Thank you!