That's a security protection, of course. To circumvent it, I'm afraid you have to install a new hard drive and install your choice of Windows or Linux on it.
It might be possible to reuse this drive by removing all partitions from it (either with Linux or via an external enclosure on another PC).
I bought i HP elitebook 840 from a estate sale. I had to buy a new charger for it but other than that it was a GREAT deal. So i thought. I'm by no means a PC tech kinda guy. Very computer illiterate. But it has bitlocker installed on it. Now i don't want recovery any existing data or information from the laptop. I just wanna be able to use it period. Is there anything i can do to bypass this? It has Windows 7 installed on it. And upon starting it up it goes straight to asking for the recovery key for this drive. Any ideas or suggestions? Like i said, i don't wanna recover anything. If possible i'd like to wipe it clean like when it was new.