Can a >2TB hard (GPT) drive be used as non-booting data drive on a non-UEFI board

Use clonezilla to make an image of your hdd then restore that image to your new drive and it would be as if nothing happened. http://clonezilla.org/
You'll have to boot clonezilla from a USB or CD in order to do this.

Alright given the new information I recommend you do the following:

1. Partition your 3TB drive in half.
2. Create the image using the software above while saving the image to the second half of the partition you just made. (Clonezilla will let you specify where you want to put the image)
3. Restore the image to the first half.
4. Once it seems everything is good, format the second partition then delete the second partition
5. Extend the first partition to cover the entire drive.

Note: If you don't have enough space then you might have to remove some of your games then just install them after the image goes down.

I recommend just messing around with it till you get what you want, because as long as you have the original you'll be fine.

Well, first, I don't think that's a good idea to have such a big OS partition anyway. A much smaller SSD for the system and the big HDD for other things would be much better.

Anyway, to answer your question:

First check if your mobo supports UEFI booting. If it does, then it is possible, but not through 'simple' meanings.

You can try to burn a DVD and install from there.

If all the above fails, read this. If still doesn't work, also see this page and scroll down till you reach the 'Windows' section. It talks about boot-loaders and such.