Ladybird87

Hi,I am trying to perform a custom install (clean install) of Windows 8 onto my computer. Entering the product key is all done but now it's asking me where I want to install Windows. It gives me two partitions to choose from but they both display this error:'Windows cannot be installed to this disk. The selected disk has an MBR partition table. On EFI systems, Windows can only be installed to GPT disks.'Does anyone know what to do about this? Formatting them doesn't do anything and the 'new' option is greyed out. Do I have to delete them to be able to create a new one?Please help! This has been driving me crazy! Thanks in advance :)