Also, 32-Bit Windows 7 won't see the full capacity of a GPT drive over 2TB, only 64-Bit?
If I were to use UEFI BIOS then all my HDD's/SSD's have to be cleaned/initialised as GPT to fully use all the functionality, e.g. seeing drives over 2TB and use of more partitions? Or could I use a program like Minitool Partition Wizard to convert the OS SSD without needing to clean/initialise?
I'm not sure about your first question, but I do think that if you want to boot from a drive larger than 2.2 TB, that it must be GPT and you must use UEFI and 64-bit. A BIOS system can't boot a GPT disk.
I rebuilt recently using UEFI on a 128 GB OS SSD, but I also have a 3 TB GPT internal storage drive. I did wipe all drives and start over, but someone on this forum within the last 2 or 3 weeks did mention a program (possibly Partition Wizard) that supposedly will do the conversion to GPT without wiping or risking data. I'd have a hard time trusting it would work and would certainly backup up all data before trying it.
I'm not sure how beneficial it is to have a UEFI installation, but I thought I'd try it.
I did have trouble.
When booting from the USB flash drive installer, I saw a bunch of menu choices, including 2 for the USB flash drive. I had to be sure to choose the one that began with the word "UEFI". Even then, I still had trouble as the Windows installation stalled with an error about the lack of a CD/DVD driver as I recall. I had no idea what that was about, but inserted the motherboard manufacturer (AsRock) driver disk into my DVD burner and was able to get by that error.
And--for unknown reasons----I could NOT use a USB flash drive installer made from a known good official Windows 7 ISO using Rufus. The installation would stop midway through the "Windows is expanding files" stage.
I instead had to use Rufus to make a USB flash drive installer, pointing Rufus to an ISO I personally made from a previously burned Win 7 installation DVD that had SP1 slipstreamed into it. That did not stall at "Windows is expanding files".
I have no idea why one method failed and the other worked.