Windows 7 'reboot and select proper boot device' problem

I believe this problem is different to previous threads on this subject.

I have a 500GB HD with a trial version of Windows 8.1 installed as GPT which I want to use as clean build of Windows 7 Pro. I used a UEFI Windows 7 USB Drive to install the OS on the GPT partition which was successfully created but as soon as other HDs were added & the system switched back on, I had a boot failure. Disconnecting the all HDs with the exception of the 500GB drive did not revert back to a previously working Windows 7.

I used AOMEI Partition Assistant to convert the GPT partition to MBR which created further problems. I booted from an MBR Windows 7 USB drive which went through the initial installation process but during the first re-boot, it didn't recognise the HD & started the installation process all over again.

I used Diskpart to clean the HD with no success.

On a reformatted MBR HD, I cloned a working Windows 7 OS onto the HD, again with no success.

Finally, on a reformatted MBR HD, I used the installation DVD which appears to have done the trick as I now have a new Windows 7 build alongside my other MBR HDs.

I'm at a complete loss to understand what has happened. I've never used UEIF before; I only went down this road because I wanted to use a 3TB disk which I believe can only be formatted in GPT.

I can't believe that GPT & MBR can't exist together because the Windows 8.1 build was GPT & was used alongside my other MBR HDs.

To further confuse the situation, I'd created a backup of the Windows 8.1 build which I restored back to the 500GB HD; this gave the same boot error as the Windows 7 build using the MBR USB drive.

badcrc said:

wightwalker said:

I booted from an MBR Windows 7 USB drive which went through the initial installation process but during the first re-boot, it didn't recognise the HD & started the installation process all over again.

This 'starting install again' can be caused by setting usb 1st in the BIOS. The best way is to leave the boot order 'as is' and select the usb via the one time boot menu, then at 1st install reboot it sees the HDD before the USB. That said, I've sometimes had to go in the BIOS to make sure the USB was lower down the list.

I normally have the HD set as the 1st boot although it was not in the 1st SATA port with other SATA drives disconnected to ensure a clean 'standalone' build.

I select the USB device during the boot sequence from the bios, so I'm pretty confident that it wasn't that.

Thanks for your suggestion.

gregrocker said:

Did you check that the UEFI install remained set as first hard drive to boot in BIOS setup when you added the other drives?

Yes

gregrocker said:

If you have MBR installs on the other hard drives which you want to boot then you need to change BIOS settings to CSM or Legacy for them to boot, too.

BIOS is set to UEFI & Legacy.

Maybe I should have connected the UEFI drive to the 1st SATA port.