If your computer was connected to a network with Active Directory, your recovery password was backed up to AD and can be recovered by contacting your AD admin. You said that the recovery key is lost but if you have the recovery password (the 48-digit number generated during BitLocker setup) you can recover the drive using the repair-bde command line tool included in Win7. Alternatively, you can create a bootable WinRE (not WinPE) DVD, which will also allow you to manage BitLocker and attempt to unlock the drive.

The computer will need to have Win7 installed. If this fails, I suggest trying to unlock the drive on another machine in case the hardware problem is on your first computer. To remove the drive encryption, use these steps: Open Start.

Type manage-bde F: -unlock -pw and type your password to unlock the drive.

Click Turn off BitLocker and enter the recovery key to unlock the drive. Right-click at the target drive and select Manage BitLocker. Note: If you forget the password, please click Enter recovery key to continue.

Type manage-bde F: -status and look under 'Key Protectors' to ensure that 'Password' appears. Select the target drive and enter the password to unlock.

My suggestion would be to first try to unlock the drive using the manage-bde utility.

Remove bitlocker