Question MBR to GPT HDD wont boot

[ViperQuibQuib]

I upgraded from a 1tb hard drive to a 3tb hard drive. Initially cloned everything over with seagate cloning program and booted up off the 3tb hard drive just fine. I wanted to be able to use the Hdd to fullest extent do I used mini tools partition wizard program to convert my OS hard drive to Gpt. Now when I boot it gets stuck right after my BIOS screen with black screen and a blinking white underscore. I check my BIOS and it had uefi selected to boot off of so im lost.

Is there a way to undo the Gpt conversion or get everything back onto my 1tb Hdd to wipe my 3tb clean without data loss?

Thank you for the help.

Specs MSI Z87 Mpower Max motherboard.
Win10 64 bit
WD velocirapter 1tb
Seagate barracuda 3tb hdd

 

[BitFlip01001]

1. Boot from the USB you installed Windows from.
2. Continue and click Repair your computer.
3. Select Troubleshoot
4. Select Command Prompt
5. Type diskpart and press Enter
6. After loading, type list disk and press Enter
7. Determine which is your HDD (disk 0 or disk 1, say it's disk 0)
8. Type select disk 0 and press Enter
9. Then type convert mbr to convert it back

Note: Type help if you want to see the rest of commands for any reason.

 

[ViperQuibQuib]

Thank you for the response! I'll try those steps when i get back to my pc and report my findings.

1. Boot from the USB you installed Windows from.
2. Continue and click Repair your computer.
3. Select Troubleshoot
4. Select Command Prompt
5. Type diskpart and press Enter
6. After loading, type list disk and press Enter
7. Determine which is your HDD and (disk 0 or disk 1, say it's disk 0)
8. Type select disk 0 and press Enter
9. Then type convert mbr to convert it back

Note: Type help if you want to see the rest of commands for any reason.