What motherboard do you have? Are you running a RAID controller?
Sounds like Windows 7 does not detect your SATA controller on your motherboard, so you will need to download the latest SATA controller drives from the motherboard's website.
When downloaded, unzip and save to a USB, start Windows 7 installation again. When you need to specify a hard drive, select load driver and select the driver on the USB.
That should solve your issue
PS - Have a look here, same issue http://www.tomshardware.com/forum/308363-30-asrock-mobo-sata-drivers-floppy-joke