TeraByte Unlimited

I want to convert from legacy CSM BIOS to UEFI with MBR2GPT. I only have one O/S on the disk, that being Windows 10. Conversion seems pretty straight forward, but I was hoping you could give me advice on what to do with the BIOS version of BootIt which sits in its own partition at the beginning of the disk.
- Should I delete the BIOS version and then do a fresh install of the UEFI version, or overwrite the BIOS version with the UEFI version?
- If so, should I be deleting the existing partition that houses the BIOS version or is it OK to preserve the existing partition and install the UEFI version into that?
- And in what order would I do the above…before or after running MB2GPT?

Use the chgdtype.tbs (Change Disk Type) script. The BIBM can be deleted, you'd then have to install BIU, but all OSes must support UEFI booting, and you'll need to reinstall the boot loaders for them in UEFI mode (for Windows you can use the fixboot.tbs (TeraByte Configure Boot) script) for Linux you'll need to install GRUB for each instance.

I do appreciate your help on this. Please confirm that this is the proper sequence, and the individual questions below in bold italics. Thanks.

Where in this sequence do I change my motherboard from CSM to UEFI?

1. Run chgdtype.tbs (Change Disk Type) script.
Do I run from within Windows on the active drive, or from the boot disk?
Do I run this for each Windows O/S on the disk?

2. Delete BIBM, then install BIU.
Do I delete the BIBM partition, or just the contents of the partition?

3. Reinstall the boot loader for each Windows O/S in UEFI mode. For Windows you can use the fixboot.tbs (TeraByte Configure Boot) script.
Do I run fixboot.tbs from the boot disk?

1 - do an entire drive image backup.

2 - boot to the windows you want default.

3 - reboot back and create some free space for the efi system partition (1G recommended for multiple windows versions).

4 - run the chgdtype.tbs script - you can let it delete BIBM.

5 - boot Windows in UEFI mode to ensure booting ok.

6 - Install BIU.

7 - run fixboot.tbs for a missing OS and reboot one-by-one to ensure each booting ok as you add them.

which of these steps need to be done with a book disk rather than from windows?

You can do them all from a boot disk.