Then the less than easy route we'll go.
I suspect that it's because the BIOS tried booting the old drive. THat old drive won't boot your new system without reinstalling Windows on that drive.
2 ways to force boot correctly
1. most systems have a F-button you can press during POST that lets you force the drive to boot from for that boot. (F11 or F8on several I've seen) Only do this if you're going to harvest your data and then remove the old drive.
2. Enter BIOS and configure your boot order, insuring the new 1TB drive is the first in the order (and if the BIOS allows, remove the old drive completely from boot potential).
EDIT: If you're struggling with these BIOS settings, reply with the make/model of your mobo and we can give you more detailed instructions...