Seagate 3TB Only showing as 746gb

[[TC]»Elmo«]

If it doesn't give you the option to convert to GPT when you right-click the drive in Disk Management, then no.

However, it might be possible to clone just the partition instead of the whole drive. You will almost certainly need to 'repair' the boot record, as it won't exist.
I've read that there's no difference to the partitions themselves just the boot record, although I've been unable to confirm this.

Edit:
What apparently does work:
Install Windows 7 on the new drive in UEFI+GPT mode (don't bother entering the key, you won't be keeping the install).
Then clone the old partition to overwrite the temporary W7 install.

Just cloning the partition as I originally suggested would probably be quicker though - you'll need to run 'BOOTFIX' or whatever the command is from the windows recovery disc when you're done.