You needed to unplug the old HD before installing Windows 7 on the new one.
In Disk Management, mark new Windows 7 installation Active, shut down, unplug old HD.
Boot the Windows 7 DVD Repair console to run Startup Repair up to 3 separate times with reboots until it writes the System boot files to Windows 7 and it starts up.
If this fails, plug back in the old HD and post back a screenshot of your full Disk Mgmt drive map with listings, using Snipping Tool in Start Menu.