Again, how is it partitioned? What is your LBA48 setting?
And regarding ThaCrip's comments:
if that hard drive is locked and the xbox dies then your 300GB hard drive is basically junk.
That's only true if you are foolish enough to not backup your EEPROM.
with the 300GB hard drive... if your planning on using ALL space on F partition then u need to use a program called "XBpartitioner"
Not true. X3CL can partition and format it with all space on F. But don't do that
! FATX starts to corrupt your partition once you get above about 250GB.