Hi wash1950, Welcome to the Windows 7 Forum!
From what I gather, you're trying to install Window 7 on your computer? I HIGHLY recommend against doing an "Upgrade" install as it will cause you nothing but problems later on down the road.
Are your hard drives set up in a RAID configuration?
Have you consulted your motherboard manual for more info if you have them in RAID?
During the Windows 7 install you'll come to a screen early on that shows the drives and their sizes and partitions, if any. There is a window below that shows an option to "Install drivers" You need to pick that section and have the driver on a thumb drive or CD or floppy disk.
The ATI AHCI controller may be in a folder by itself on the driver disk or when you download the driver in a ZIP format and decompress it. Sometimes they'll just be a folder with; Floppy 32 bit or Floppy 64 bit labels on them.
Make sure the AHCI options are enabled in the BIOS on your motherboard too.