Why convert a GPT disk to an MBR disk?
Although most customers choose GPT as the disk style due to its more advantages over MBR before the first use, sometimes they might need to convert a GPT disk into an MBR disk. The most important reasons should be the limitations of OS support on GPT disk (not all operating systems can be installed on GPT disk):
1. The early operating systems including Windows 2000, Windows MS-DOS/NT, Windows 95/98, Windows Vista 32-bit and XP 32-bit are not unable to read, write and boot from a GPT disk.
2. All versions of Windows Vista/XP/7/8/10 and Windows Server 2003/2008/2012/2016 can use GPT disk to store data. But only 64-bit editions on UEFI-based systems can be used as system disks.
If you try to install Windows 7 32-bit on a GPT disk, you will fail with an error message "Windows cannot be installed to this disk. The selected disk is of the GPT partition style". Therefore, you need to convert to MBR disk
Option “Convert to MBR disk” not available in Disk Management
When it comes to converting the disk to MBR from GPT, you might immediately turn to Disk Management - a built-in disk/partition management tool for windows. But when you run it and right-click the GPT disk, you might find the option “convert to MBR disk” not available or clickable, which prevents you from converting it to MBR disk.
The main cause might be there are partitions on the chosen disk. In disk management, you can only convert an empty disk (without any partitions) to MBR or GPT disk. So you can try to delete all existing partitions and then convert to it to MBR disk.
Convert to MBR disk via Diskpart (require deleting all partitions)
If you cannot convert GPT to MBR in Disk Management successfully even after removing the volumes on it, you can use Diskpart utility. But this method also requires you to delete partitions on the GPT disk first of all, so back up data that is important in advance.
First, click "Search" box on the desktop and input "cmd" in it, right click the program and select “Run as Administrator” to open the prompt window.
Then type the following commands in turn and press Enter after each one. (Here we take converting disk 1 to MBR as an example)
Diskpart->list disk->select disk 1->clean->convert mbr
Easiest way to convert GPT to MBR without deleting partitions/losing data
As you can see, deleting all partitions on the chosen disk is a must step when you want to convert it to GPT or MBR in Disk Management and Diskpart. If you store lots of important data within the disk, you have to back up data, then delete partitions and finally restore them after conversion completed, quite time-consuming and troublesome, right?
So you might wonder is there another way to convert a GPT disk to MBR without deleting volumes? Yes, AOMEI Partition Assistant can satisfy you best. It is able to help you get rid of convert to MBR disk not available problem in Windows 10/8/7/XP/Vista. Moreover, it also supports converting GPT to MBR and vice versa no matter whether there are partitions on the target disk.
Below we will show you how to convert a GPT disk to MBR without deleting all partitions in Windows 10.
Step 1. Download the freeware. Install and launch it, right click the GPT disk and choose "Convert to MBR Disk".
Step 2. When the message “Are you sure to convert the selected disk from GPT to MBR disk” pops out, click "OK" to continue.
Step 3. Hit on "Apply" to commit the GPT to MBR conversion.
Because the partition size of MBR disk is up to 2TB, it is not advised to convert a GPT disk, which is over 2TB, to MBR. If you force convert it to MBR, you might meet hard drive showing wrong capacity issue then.
Although this method won’t require you to delete partitions first, we still suggest that you should back up disk to avoid data loss resulted from some accidents like a sudden power failure.
AOMEI Partition Assistant is an effective tool to solve convert to MBR disk not available issue when you don’t want to clean the disk first. Besides, it develops a new function named NTFS to FAT32 Converter, which enables you to convert NTFS to FAT32 and vice versa without causing data loss. So definitely worth your trying