Start>Run>type DISKMGMT.MSC and press OK.
Rightclick the "G" drive and click "Change Drive Letter and Paths".
Are you sure you want to change the drive letter? You may have other
peripherals that use the "F" drive such as a printer, card reader, MP3
player, etc. You may want to keep it as "G" to avoid future drive
complications,
for it looks like your system wants it as "G". Microsoft also recommends that
you use drive letters further down the alphabet for external drives starting
with "H".