Convert GPT disk to MBR HELP!

[kevzz010]

So I've been searching for a way to do this and I gave up. I really don't get it so I need you all's help. So my laptop is Lenovo y40 and it had windows 8 in it. Now I've been wanting to install windows 7 to it (cause win8 sucks) but I have to convert the disk from gpt to mbr first. So I have no clue why but the disk has a lot of partition, 3 of them are actually hidden, and I deleted some of the other partitions that I can ( didn't want to touch the others cause it says OEM/SYSTEM Reserved, not sure what it is for). Now I downloaded this software called AOMEI partition assistant to convert my gpt disk to mbr but the options are GREYED OUT. I'm guessing the reason is the one I'm trying to convert has the Windows files in it. So, what am I suppose to do now? How can I convert the disk to MBR? I tried the manual stuff like cmd/windows interface but even cmd gave me an error.
I'm guessing I have to completely format this hard drive then convert it to mbr but then how can I convert it without windows?

Any ideas/advice?

 

[kevzz010]

UPDATE: Ok so at Windows 7 Installation Wizard I hit Shift+f10 and I was able to convert the disk to mbr through command prompt. It said it was successful. After windows 7 64bit installation though, the drive was converted back to GPT? Now I have no clue what's going on. My Bios boot mode is set to Legacy Mode, then UEFI First. Not sure if it's because of it or maybe I need to make a partition or something? What makes it convert back to GPT? Any help would be greatly appreciated

 

[Christopher Sadlowski]

UPDATE: Ok so at Windows 7 Installation Wizard I hit Shift+f10 and I was able to convert the disk to mbr through command prompt. It said it was successful. After windows 7 64bit installation though, the drive was converted back to GPT? Now I have no clue what's going on. My Bios boot mode is set to Legacy Mode, then UEFI First. Not sure if it's because of it or maybe I need to make a partition or something? What makes it convert back to GPT? Any help would be greatly appreciated

I'm actually in the middle of trying to figure out this MBR/GPT thing myself. I know your thread is a bit old but no one has replied and I'm not sure if you've gotten your situation fixed. GPT is the format that's used by UEFI to store the critical Windows boot files. It's a newer method that replaces the BIOS of yore. Apparently your copy of Windows 8 has been installed at the factory under UEFI mode, and when that happens the hard drive is formatted in GPT so UEFI can access the boot files. AOEMI (which I also checked out) can only show you what it can possibly do with the free trial. It won't do anything until you pay for it and it's probably not worth it. Using the command prompt to mess around with trying to change the disc format from MBR to GPT, the other way around, or switching around willy nilly is very dangerous and should not be attempted. You can seriously mess up the files that Winodws needs to load and then you'll be forced to wipe the drive clean and start everything all over. And with manufacturer recovery discs it can be VERY difficult to correct issues that arise. Even the retail version of Windows can be tough to control if something goes wrong.

I notice that you said that in your BIOS, UEFI is set to load first THEN Legacy Mode second. Because you have these options it means your motherboard can allow Windows to run in UEFI or BIOS; they both control the boot process but in very different ways and they are not compatible with each other. Windows cannot run partly in UEFI and partly in BIOS.

What this all comes down to it that basically your motherboard will fire up UEFI boot sequences first and then will allow other things to run in BIOS second. Windows 7 and Windows 8 can run in UEFI quite happily, while other components of the computer can only run in BIOS. The motherboard is basically able to direct the flow of traffic between both of the firmware requirements of the components of the computer. For example, UEFI boots up Windows and BIOS boots up your Ethernet controller. If it sounds complicated, it is.

You SHOULD be able to install Windows 7 to a hard drive that is in the GPT format. It can and will run in the UEFI environment. When you used the command prompt to change the disc format into the older MBR (Master Boot Record, which is accessed via BIOS) it reverted back because you still have the Windows 8 System partition and apparently the new Windows 7 partition. If you're really serious about removing Windows 8, the "OEM/SYSTEM" can probably be deleted, but with a working copy of Windows 7 installed and operational I would just leave it alone. It can be easy to delete the wrong partition and force you to start everything over yet again! I'm going to assume that Windows 7 is working since it was able to be installed? I suggest you do NOT try to change the format of the disc anymore if Windows 7 is working correctly. The hard drive is in GPT format because it's using the new UEFI firmware to boot up and run. GPT is the newest architecture, MBR is the old format that is used by the ancient BIOS systems. I hope you found this VERY long and convoluted post helpful.

 

[mchldpy]

If You have no desire or intentions (in the near future at least) of of reverting back to 8/8.1 then, for Windows to successfully change a disk from one partition table format to the other, ALL partitions must be deleted and the whole disk turned into unallocated space. Then you can put the disk into another computer running Vista (or higher) and use Windows Native/internal disk utility in Disk Management (NOT the disk utility present on a Windows install disk) and re-initialize the disk as either type of partition table. I have never used the command prompt to perform these steps as the M/S article I was reading did not discuss using the cmd prompt. I would ASS-U-ME that the cmd prompt would not work if the whole disk was not 100% unallocated space. I have used this process successfully on "Basic" HDD (no Dynamic/Raid or SSD) type of disk.

michael clyde

 

[floydstime]

Alright so I worked on this for about a week and as I am typing ... I have successfully converted GPT to MBR. This is how I did it...

1. Back up existing GPT drive. (I used Acronis).
2. Install windows 10/8/7 on a blank new drive formatted as MBR. You can use whatever method you like to format as MBE, i.e. diskpart, EaseUS, etc... It doesn't matter because you have already backed up your other drive.
3. Once you install Windows 10/8/7 formatted as MBR, then you have the layout already.
4. Restore your backed up drive C: drive ONLY, not the whole disk or any other partitions... ONLY the C: drive.
What this does is replace the MBR drive you just installed with your backed up C: drive.
Now it won't boot. But here is what you do.
5. Plug in the USB/DVD of Windows 10/8/7 that you installed and select repair.
6. Use the repair tools to go to command prompt.
7. type bootrec /fixmbr
8. type bootrec /fixboot
9. type bootrec /scanos
10. type bootrec /rebuildbcd
At this point you will probably have an error that says it can't find the system disk.
11. type bcdboot C:/Windows /s C:
12. Restart your PC.
This worked for me. If it doesn't boot, you can try /fixmbr /fixboot /scanos /rebuildbcd and try again.
Another thing you can try is to use diskpart to set the boot volume as active. I don't remember all the steps, but I am sure there are some guides out there, or maybe someone else can chime in. Hope this helps, let me know if it works for you.