You need to repartition it first to an MBR partition scheme, then you can format it. Of course sometimes, Windows being the American tourist of operating systems, expecting everyone else in the world to speak the same language, you need to use a computer running a different OS to actually get to the point where you can alter the partition table.
So worst case scenario, take it back to your friend's computer, and use Disk Utility to create a new FAT partition which you should then be able to redo as NTFS on your computer.
Also, just FYI, it's Mac, not MAC, and Vista, not VISTA. It's a minor thing, but MAC typically is a networking term referring to a unique code that every network card has, so it could lead to some confusion if you keep capitalizing it all the time.
Being a good guy I lent my external HD to a friend experiencing issues. It was decided to use the external HD to backup her MAC, but first she needed to reformat the external HD. After receiving it back and using with my VISTA I cannot see this drive anymore. I'm running Vista and have gone into Disk Management and can see the disk but cannot format or change in any way. Is this buggered or what??? Ideally I'm guessing its got to come back to a NTFS file system also. Look forward to receiving any assistance!

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