windows cannot be installed on this disk. The selected disk is of the GPT partition style.

So I was asked to downgrade a Windows 8 Laptop to Windows 7. Having changed the BIOS options to allow me to install Windows I came across another problem. When asking where to install Windows 7, I selected the appropriate hard disk, but it through up "windows cannot be installed on this disk. The selected disk is of the GPT partition style". This was quite worrying as I had just deleted any OS already on the hard drive.

The solution though it pretty simple. When you have booted the CD into the Windows install and are waiting at the screen whowing the available hard drives..

First press SHIFT + F10

When the dos box comes up, type in DISKPART

Now type list and you will be given a list of hard drives available. 

Type in select # where # is the disk number given in the list.

It should say "Disk 0 is selected" or words to that effect.

Now type in clean

This will wipe all the configuration information from the disk, including the stuff that tells it that it is a GPT partition.

Once this is complete type in exit

Then close the dos box and click on the refresh button under the hard drive options.

You should now be able to  install to that hard drive. 

If not, download G-Parted and use that to make the hard drive an NTFS drive.