This may be because your PC does RAID on its HDD(s). It may not be due to the DVD/CD drive at all. If you think about it, you would not have gotten this far (to read the OS install disk) if the DVD/CD driver was not working/installed. I had this problem with my Gateway LX6810-01 computer. Some people have posted that if you make your IDE DVD/CD drive slave instead of master, it would not give this message. However, on my PC, I cannot do that in the BIOS.
I downloaded the motherboard chipset driver package from Gateway.com, unzipped it and put it on a USB flash drive. Just before clicking "Install Now" for Vista, I inserted the USB flash drive. When the "A required cd/dvd drive device driver is missing" error message appeared, I browsed to where I had stored the driver files and selected the top directory yielded by the unzip. The install program recognized the RAID and SATA controllers for the motherboard. (I asked it to display only compatible drivers.) The drivers were installed, and the rest of the error message no longer appeared.