Reset windows 7 local admin password on encrypted drive

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http://serverfault.com – I have lost administrator password on a windows 7 laptop running bitlocker. I know bitlocker recovery password for this PC and can access BIOS setup. I need to reset administrator password without removing HDD from the laptop. Is there a way to do so without having to decrypt the drive first ? If not, how can I decrypt the drive given the fact that I cannot login as admin to the machine ? I am considering to boot Linux on a USB drive and run a copy of Windows 7 from Linux via Virtual box. Then try to decrypt laptop HDD from this copy of Windows 7. I hope there is an easier way... If not, (HowTos)