Change GPT TO NTFS

How to reformat HD from GPT partitions to NTFS partitions for Windows 7,8 installation?

If you want to install Windows 7 on a brand new machine that is currently running windows 8.

During running of OS setup, The error message says Windows cannot be installed on GPT partitions. Windows must be installed on an NTFS 

First of all GPT and NTFS are two different items.

A disk on a modern desktop is usually partitioned in either MBR or GPT.

Those partitions are then formatted with a filesystem, such as FAT, ext2, NTFS, ...

You can install windows 7 by either:

Using an UEFI equipped motherboard, booting the windows DVD, partitioning the drive with GPT and installing windows on a NTFS partition.

Using a BIOS equipped motherboard, booting the windows DVD, partitioning the drive with a MBR and installing windows on a NTFS partition.

If you boot with a old fashioned BIOS and try to install windows on a GPT partitioned disk then you will get an error. This is probably what is happening in your case. (An assumption since you did not specify the precise error you get).

You solve that, either wipe the old disk and then reinstall, or change your motherboard to the right boot mode. (Some, not all, support both EUFI and BIOS modes).

TO WIPE YOUR HARD DISK: 

Boot the windows DVD, press SHIFT and F10 to get a command prompt and use diskpart with the clean option. If you have multiple harddisks then make sure you select the correct one.

Use any Windows 7 or 8 startup disk. When you're asked what hard drive to install to, press Shift+F10 and a Command Prompt window will appear.

Enter the following commands:

DISKPART

LIST DISK

SELECT DISK #

(Where # is the number you saw in the previous step.)

CLEAN

CONVERT MBR

CREATE PARTITION PRIMARY SIZE=50000

(The size is in MB, so enter the amount that you want to use for your system partition.)

FORMAT FS NTFS LABEL "SYSTEM" QUICK

Close the Command Prompt, refresh the installer window and it should show the new partition layout. 

Select the partition you created to install Windows 7 or 8, and click Next.

WARNING: COMPLETE HARD DISK WILL BE CONVERTED AND ALL DATA WILL BE LOST.

GPT is a modern partition table. Contrary NTFS is a filesystem, which is different from a partition table.

Windows 7 needs the old MSDOS partition table and a partition formated with the NTFS filesystem.

As you already have several partitions on the drive you need to reformat the whole drive and use the MSDOS partition table. 

The disadvantage is that MSDOS partition tables only support 4 primary partitions, one of those can be made into an extended partition that supports more logical partitions, but not every OS is able to boot from such a logical partition.

There is no way I know of to convert a drive on the fly from one table to another. Back up your data and try it out. Or as an alternative buy a second drive, you can then use MSDOS partition tables on it and keep the GPT on the other one.

REFERENCE:

http://superuser.com/questions/515891/how-to-reformat-hd-from-gpt-partitions-to-ntfs-partitions-for-windows-7-install