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Redeploy the OS (Windows 10) with boot mode set to UEFI

I have a spare Lenovo thinkcentre that I have been working on for several weeks with an issue involving Bitlocker encryption and TPM.  Have tried too many things to mention and now am to a point where the tech I am working with has advised that I need to "change the default boot mode to UEFI (currently set on Auto or Legacy) and redeploy the OS (Windows 10).  Supposedly TPM 2.0 should work with the UEFI boot on a GPT partition.  When I change the boot mode to UEFI in the BIOS and restart I get an error 1962 - no operating system found.  Any guidance you can provide on how to deploy the OS with the default boot mode set to UEFI would be appreciated.  Thank you
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Author

Commented:
I will give it a try!  Thank you!
Distinguished Expert 2019

Commented:

If you care about keeping your OS like it is, with all files, programs and settings kept, do the following:


-Create a backup image of your c: drive and eventual other partitions that you have

-boot a setup stick in uefi boot mode. Start windows setup right to the language selection, press shift F10 to bring up a command prompt and there, launch one after the other:

diskpart
list disk
sel disk x
clean

x would be the number of your boot disk (in case you have more then one disk, else, it is always 0)

-close the command prompt and install windows clean

-restore your image of c: over the newly installed c:


Done! You know have converted to UEFI/GPT and may use bitlocker with TPM 2.0.

--

That said, what you could also try in case you have windows 10 v1703 or newer, is to use the command

mbr2gpt.exe, which will convert your drive to GPT at runtime, keeping anything. Just have a backup ready, in case something unintended happens.

Author

Commented:
Thank you both for your help.  I was unable to get the OS to install in the UEFI boot mode.  The OS started to install then I received an error.  Since the PC is fairly old, I am just going to decommission it and replace it.  Thanks again for your help.