Unlock Bitlocker Drive Encryption

[Peterthe1]

When trying to open my Seagate 2TB USB harddrive the following message appears.
Recovery error. Error recovering disc F: A recovery key was not found on this drive. The drive cannot be unlocked. At the top of the window the message heading is BitLocker Drive Encryption (F. The HDD was running fine on a windows 8.1 system. It previously ran on a windows 7 system. When taking it off the windows 8 and changing back to the windows 7 computer the above message appeared. It still runs fine on the windows 8 system I have never put any BitLocker software on the HDD.How do I fix this? All constructive help welcome.
PS. I'm not a computer boffin. So please keep it as simple as possible

 

[Agent Smith]

You must have used Bitlocker in Windows 8. If the data is not important you can format the drive in Windows 7. Go to the My Computer icon/ right click the drive (make damn sure it's the right drive) and select format.

If the drive was encrypted with Bitlocker and you have data that you want. Put it back in the Windows 7 computer and do the following:

1. Shut down both computers.
2. Remove the hard disk from the inoperable computer and install it in the host computer.
3. Start the host computer and log on.
4. Open Bitlocker Drive Encryption by clicking the Start button
   
   , clicking Control Panel, clicking Security, and then clicking Bitlocker Drive Encryption.*
   
   If you are prompted for an administrator password or confirmation, type the password or provide confirmation.
5. The transferred drive will be indicated in the list of drives as a Locked Volume. Click the Unlock volume link, and then follow the instructions on the screen.

http://windows.microsoft.com/en-us/...computer-locked-by-bitlocker-drive-encryption