Hi thanks for using Just Answer.com Could you please tell me what version of the MAC OSX you are using? IE 10.1 10.2 .... 10.6
Also just so its clear you want to completely format this hard drive? Have you backed up all your files as re partitioning the drive will erase the information on it
Please let me know when you are in the chat thanks
Also can you tell me if your hard drive already has been partitioned once before this attempt to partition as it can affect the steps needed to solve this question.
im using mac 10.6.8 i have back up my drive thru time machine but it wont let me partition the hard drive