Changing motherboards with same OS installation is a bad idea. Copy back whatever you need in that drive using the old setup with Intel (hope this would work). Or you could use an external USB enclosure with another PC but recovering contents on your profile will be a bit of pain. (Folder Rights – You may have to take the ownership on Security Tab)
Once you’re happy, setup Win7 booting from DVD. Choose Advanced Disk Option and delete all existing partitions and create new partition(s) and install Win7. Tip: Create 600GB partition for Win7 and create another for your data for the remaining free space.
"Still, I was under the impression that 64-bit OS’s were or are better able to recognize and manage TB sized HD’s.
Is this incorrect?"
I don’t see any advantage on 64bit OS for larger drives. But it can address larger RAM (efficiently) over 32bit OS. (As I can remember it should be 256GB Max).
WinXP cannot use TB drives unless it is SP2 or SP3. Microsoft is discontinuing its support for SP1 & 2 in the near future. If someone elect to use XP any longer, he needs to update to SP3.