Win10 won't boot on newer computers

[Trozza]

Hi,
I installed windows 10 on a portable hard drive with WinToUSB using the Bios/UEFI method. It worked on my older PC (about 8 years old), and on my works old laptop (no idea how old). I tried it on my wife's new laptop (roughly 3 months old), it wouldn't boot, it just goes to a blank/black screen. My work gave me a new HP zbook mobile workstation to replace my old laptop, and it too won't boot from the portable hard drive. After I select the USB hdd as the boot drive, it just goes to a black screen. After a few minutes i try hitting a few keys on the keyboard and it just starts beeping at me. I don't get any windows boot logos or warnings. I take it back to my older PC and it boots fine.

I had a look inside bios (luckily they didn't lock it down) and I can see that it's setup to boot in legacy mode and not UEFI. However, just to try a few different options,

• I setup the hard drive to boot as UEFI and ran it through the process again. When I select the USB hard drive on my laptop, it just ignores it and goes to the next bootable option and starts booting up the internal hard drive.
  
• I setup the hard drive to boot in legacy/BIOS mode and ran it through the process again. When I select the USB hard drive on my laptop, I just get the same blank/black screen as before.
  

I'm at a loss as to what to do, as it doesn't provide me with any error messages.

Any ideas on what I can test?

Thanks,
Troz