using GPT on your OS drive is only necessary if you are using a drive that is greater than 2.25TBWindows 7 installer will detect GPT and prompt you to change the disk partition scheme to MBR or NTFS in order to install Windows 7. Installation continue will remain greyed out until you do.
Are you using an EFI supported Motherboard running the port controller in AHCI mode?Formating the primary drive GPT from the get go or starting with a blank partition leaving Windows 7 Pro & Ultimate to do it via diskpart, setup will not proceed until you change the partition scheme to NTFS or MBR. Continue installation / setup remains greyed out even though you can clearly see the partition formated GPT and you receive the following message...
Windows cannot be installed to Disk 0 Partition 1
Click on "show details"
"Windows cannot be installed to this disk. The selected disk is of the GPT partition style."
Intel and MSI both offer EFI support desktop motherboards, I am running the Intel DP55KG motherboard, this is also the only system that I have been able to install OS on GPTNo, EFI has not entered the PC business laptop and desktop world yet. It is limited to mostly blade and enterprise servers.