This Windows pre-boot execution environment ISO can be used on encrypted HP drives to recover the data or fix the Windows install. You’ll need to know the decryption key or the encryption login password for a user on the machine.
SDWinPEx64.iso ordinarily needs to be obtained from HP support, but I’ve hosted a copy here for those who don’t have a valid support subscription. You can get it at http://phil.lavin.me.uk/downloads/SDWinPEx64.iso
There’s a decent guide here for fixing a corrupted BCD: http://tom.meinlschmidt.org/2015/06/16/bcd-boot-troubles-and-winmagic-encryption/