Is there any was to easily tell how much free space is on each partition of the xbox hard drive? I have the original drive in the box, and I want to know when I get close to the limit for partition E: Is there a way I can map the drive as a network drive in windows and then use some windows tools to give me the total used and unused space on the drive? Or is there an ftp command that supports this information?

It tells you in the hardisk menu. Look at it then add a game and look again. It tells you the freespace, except its in bytes