check the boot ini file
[boot loader]
timeout=30
default=multi(0)disk(0)rdisk(0)partition(1)\WINDOWS
[operating systems]
multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="Microsoft Windows XP Professional" /fastdetect
if this is on the G drive you may be ok and just need to use the
default above
swap drives around make sure the master is G it will now be C
this is for clean boot seq.
if the boot.ini is on C you may need more help
look in disk management and see where the boot and system drive is
g should be the system drive
just remember any programs that ran from this drive or the other when you change they will not run XP drive letter change