Did you delete the existing partition? If you delete all partitions on the drive, you should end up with all unallocated space, then you should be able to format, or just tell Windows to install on the drive and it will format it. BTW a "full" format is recommended in this situation (instead of a "quick" format), even though it's a lot slower, especially if you had Windows on it before (Google it for the long explanation why). Also try a different SATA cable and port if possible, cables can go bad.