When you run the Windows 7 Setup program on a computer with a single, raw hard disk, Setup presents you with a screen identifying the disk and its size. If you want to create a single volume encompassing the entire disk, click Next to proceed. Otherwise click Drive Options (Advanced). On the screen that follows, you can use the Size control to specify how large a volume you want to create for your Windows installation.

If you decide not to use the entire disk for Windows, you can create additional volumes from within the Setup program. But there's no particular need to do this. After you have installed Windows, you can use Disk Management to create one or more additional volumes in the unallocated space remaining on the disk.