This worked for us!
To install Windows 7 on a pre-installed Windows 8 computer
Laptop Acer Aspire V3-771G
Many new Windows8 pre-installed systems will not boot from CdRom.
To enable booting from CdRom you need to get into the Bios of your computer.
In this case (Acer laptop), press and hold the F2 key while restarting the system.
Restarting is important; Shutdown/startup will not work with the F2 key.
Once in the Bios, go to the Boot section and set the CdROm device as primary boot device.
Disable UEFI boot
Exit with save & reboot
Startup the computer using a 3rd party boot manager that supports GPT/MBR boot record management.
In this case we used an Acronis Boot Disk (created with Acronis True Image 2013).
Install - step 1 (Acronis)
Windows 7 will only install on a disk/partition with a MBR (Master Boot Record) partition table
- From the Acronis boot menu, select True Image
- Choose Tools & Utilities from the left menu and Add New Disk -> Next
- Select your hard disk from the list -> Next
- Ok to confirm deletion of all data and start paritioning
--> ### double check that you have the correct disk, to prevent data loss !! ###
- Select the required disk initialization method: MBR -> Next
- Create partition(s) -> Next
- Specify settings for the partition being created -> Accept
- Proceed. MBR partition table will be created on the new disk.
- Finish. Exit True image, remove the Acronis boot CD and restart your computer, using a Windows7 boot CD
Install - step 2 (Windows)
Install Windows7 on the newly created MBR disk