Disappeared Partition After Install The Windows 7?

I'm using a 500GB hard drive that is split in to 2 partitions. The primary partition is 50GB, primarily for the OS. The second is the rest of the usable space on the drive, and has all the photos, documents, etc stored on the computer. Today I decided to finally install the Windows 7 RC that I've had sitting around. I moved over any important information on the C drive, the primary partition, over to the D drive, the larger partition, popped the disk in, and in setup, formatted the C drive. I finished the install without incident, but upon getting in to Windows 7, found my second, larger partition, had vanished.