You can use the Windows 7 disk to wipe the drive out and run the install, then run the upgrade install to Windows 8 immediately after the 7 install is done. Be sure to back up your data first though. You cannot, as you are suggesting, install Windows 7 as though it is an upgrade overtop of Windows 8. You must wipe the drive out first to do that.
Ok thanks. I wasn't sure if I could use the win 7 disc to wipe the drive while installing or if I needed to erase win 8 before I even put in the win 7 disc.
I dont really have much to save on comp since I installed win 8 and couldn't get full access to it since it was an upgrade only.