BitLocker issue. Recovery Key is required on each startup after installing secondary OS
Solution 1:
You need to log into Windows 7, suspend Bitlocker (no need to disable your TPM), then reboot your computer into Windows 7 again (and reenable Bitlocker if it doesn't automatically do it). This will "reset" Bitlocker to understand your new dual-boot configuration. Once you've done this, you should not need to enter your recovery key the next time you boot into Windows 7.