To install Windows 7, you will need to make sure:
1. That you have made recovery media for windows 8 (Flash drive or DVD) BEFORE you start. Windows 7 install WILL DESTROY the recovery partition.
2. Boot your Windows 7 DVD in legacy (NOT UEFI) mode, F12 at powerup. Go into the drive partition manager.
3. Delete ALL partitions on the hard drive.
4. Create at least a C: partition
5. Install Windows 7, followed by your chipset driver, followed by all your other drivers.
6. Run Windows update to install all the latest patches and updates.