Did your computer create another partition? You can check this by going to Control Panel>Administrative Tools>Computer Management. Click on Disk Management and look on the bottom half of the screen. If you see a box that says a disk size then says Unallocated, right click on it and select New Partition. Follow the steps and keep most of the options selected. The only option that you should change is the partiton size.
Is your current filesystem set to NTFS? To check, go to My Computer, single-click on your hard drive, and look in the sidebar. If it isn't NTFS, go the the command prompt (Start>Run>cmd.exe) and type in convert (drive letter) fs:/ntfs. If i'm not correct, use Help and Support (search NTFS coversion or something along the lines of that). This process can take a while, depending on how much hard drive space you have used (5 GB or more usually takes 5 minutes or more).
If none of these remedies work, I'm sorry.