A little more information would be helpful. Did you want to install an OS on this drive or is this drive just an extra storage thing? If you are installing an OS, whatever OS you choose will have a partitioning program as part of the installation. If this is an extra storage drive, then repartitioning will depend on what OS you are running. Start>Run>diskmgmt.msc will open up the Disk Management application built into Windows. You should be able to do what you want from there. (Right click on the free space representation and there should be a "Create partition" option, I think). Another option for Windows would be running diskpart from the command prompt (although you'll probably have to read up a little on in first).