Booting USB installation media on a UEFI system.

Whilst not related to this Windows 10 forum, I had major problems using a UEFI Windows 7 USB boot disk.

The initial installation worked perfectly on my standalone HD allowing me to install updates & applications until I added my MBR Data HDs. The new build was then not recognised with the following error message: 'Reboot & Select proper Boot device or insert Boot Media in selected Boot deice & press a key'.

It was still not recognised even after I had removed all the MBR HDs & I could see no obvious way to repair the build other than a re-install which replicated the problem.

Converting the GPT HD to MBR & re-installing Windows 7 created a situation where files were coped to the HD but on the first re-boot, the same error message was repeated.

Even cloning a working Windows 7 build to this HD resulted in the same error.

I used AOMEI Partition Assistant & then Diskpart/Clean to initialise the HD but no success.

I then used the Windows installation DVD & to my surprise the installation was a success.

No idea what was going on because previously that HD had a build of Windows 8.1 on GPT partition which worked OK; even restoring that build back to the HD failed.

Can only conclude that are problems if you have a mix of GPT & MBR HDs with OS on them.

feherneoh said:

Problem is if your motherboard is not forced to boot only UEFI or only CSM

Motherboard is a dual UEFI BIOS set to UEFI & Legacy.

When I installed Windows 8.1, the only problem I had was that I had to let the installation determine the HD configuration was was from previously MBR to GPT. All this was done with making no changes to the BIOS & I could boot successfully between Windows 7 (MBR), Window 10 (MBR) & Windows 8.1 (GPT); these being the 3 OSs I had on the system.

The problem came when I created a UEFI boot USB drive to see how easy it would be do a UEFI Windows 7 installation on the HD with Windows 8.1 previously installed - I was considering buying a 3TB Western Digital Black HD which I believe would have to be formatted as GPT to utilise the full 3TB. The installation was OK during the initial build when just 1 HD (GPT) was connected. When I connected the MBR data HDs, the UEFI version of Windows 7 refused to boot even after I had removed the MBR HDs. I found no way to repair the UEFI installation from the UEFI boot USB.

Re-installing the UEFI version of Windows 7 was fine again until the MBR data HDs were added to the system.

Realising that, for whatever reason this was not going to work, I then converted the GPT disk back to MBR to install Windows 7 which was when the installation got into a loop & at the first reboot started to load Windows into memory again. If, during the reboot, I used the BIOS boot to select the HD then the error message 'Reboot & Select proper Boot device or insert Boot Media in selected Boot deice & press a key' was presented.

It didn't matter what I did, nothing appeared to work until, in desperation, I reverted to the Windows 7 installation DVD.