If you see This PC doesn't support entering a BitLocker recovery password during startup, enable WinRE, tweak Group Policy, ...

The BitLocker encryption built into higher-end versions of Windows Vista goes a long way toward locking out intruders at the boot-drive level, but it's neither 100% hassle-free nor 100% secure.

Input the BitLocker recovery key. Wait until the unlock period expires, and then enter the correct PIN. Reinstall the operating system, and then reset the TPM chip.