Windows 7: 1TB Fat 32 external Hard Drive randomly un-mounts when copying files

So I have a 1TB Fat32 USB 2.0 Hard Drive that I have connected to my Xbox 360 to play music and videos on my TV. (Streaming from the back room is unreliable, I formatted it as Fat32 because Xbox won't recognise anything else).



Works great with the xbox. However when I transfer files to/from my Windows 7 PC, it will randomly unmount then remount. There is no consistancy as to when it happens. Sometimes files will transfer without a hitch, sometimes not.

Now the drive will always unmount when I run a disk check or try to defrag.
Any ideas as to whats happening?

Also, I've been plugging in and powering up the drive before I boot the PC, as plugging in after the PC was powered up seemed to make the drive act buggy.

Any help will be greatly appreciated!