Windows 7 Professional cannot encrypt the system drive (C:) using BitLocker. It only supports BitLocker To Go — encryption of removable drives (USB, external HDDs).
Native is not included in Windows 7 Professional . While later versions like Windows 10 and 11 include BitLocker in their "Pro" editions, Microsoft restricted this feature in Windows 7 to only the Ultimate and Enterprise editions. bitlocker windows 7 professional
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