The secret partition is not involved with bitlocker. Bitlocker is on the C: disk with the rest of the OS. The secret partition is created so that if you decide to encrypt the OS drive, the boot files remain unencrypted to prevent the boot from failing. If you're not going to encrypt the OS, the extra partition is superfluous.
Cloning the OS creates a different problem. The BCD describes the whereabouts of the boot loader in each entry by UID. That UID is the long complex number you see in EasyBCD detailed mode, which Easy translates into a letter for you for ease of understanding. There are no disk letters in the BCD. That UID describes the unique signature of the HDD and the start position of the partition.
If you clone an OS, then the disk signature of the new HDD is different (they're all uniquely coded during manufacture), so the BCD entry will not find the new clone because it refers to the old HDD.
Simplest thing to do is to clone the OS to the new HDD, disconnect the old HDD, boot the W7 DVD and run "startup repair" on the clone three times (probably) till the HDD can boot unaided by the DVD. Then reconnect the old HDD, leaving the new one first in the BIOS boot sequence.
Add any dual boot entries to the new OS's BCD with EasyBCD.