|"he discovered that the computer he has does not support Windows 7 at all and that only Windows 8 will work"..."Someone told him that the product key is probably built into the BIOS"|
You're a certified tech & you actually believe that? The BIOS does NOT contain the Windows Product Key. And there ARE Win7 drivers available for all the devices (chipset, graphics, audio, network, etc), you just have to spend a little time looking for them. They're available from HP for slightly older systems that used that exact same motherboard with Win7, the Pavilion p6-2171a for example.
Your friend totally eff'd up by wiping out all the partitions before creating the Win8 recovery disks. If he didn't like Win8, why would you suggest reinstalling it? Go with Win7 & spend the time to find the correct drivers.
"he kept getting BSODs"
Spend a little more time troubleshooting, as I said, that system DOES support Win7. Did you do a search for info on the STOP code & error message & confirm that the graphics or graphics drivers were the cause? Did you test the RAM with memtest86?