You can only use a trick: start windows2go (Windows 10) from a USB stick, encrypt c: of win7 using a password and the encryption algorithm AES256 (NOT XTS_AES256, aka the "new" method, since win7 does not work with it). Done.
Else, there is no way with win7 pro since it does not support BL on its own.
Bitlocker on windows 7 Pro

Hi support,
How can i be able to enable bitlocker on windows 7 pro?
3 answers
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MTG 911 Reputation points
2020-12-15T14:11:13.057+00:00 Jenny Feng 13,736 Reputation points2020-12-16T02:28:56.19+00:00 @Michael Ombima
Hi,BitLocker is unavailable for Windows 7 Pro and it cannot be downloaded and installed. It is available for Windows 7 Ultimate and Windows 7 Enterprise editions
For more information, you may refer to the following link:
https://learn.microsoft.com/en-us/previous-versions/windows/it-pro/windows-7/dd835565(v=ws.10)?redirectedfrom=MSDNHope above information can help you.
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Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.S.Sengupta 5,871 Reputation points MVP2021-02-04T13:35:09.497+00:00 BitLocker is unavailable for Windows 7 Professional and it cannot be downloaded and installed. It is available for Windows 7 Ultimate and Windows 7 Enterprise editions.
Hi,
I tried both the methods and it did not work.Still searching for a solution to see if it will work.
Kind Regards,
Michael
Michael, what did you you try and to what result. You need to provide details.
I know that my suggestion works since I have used it.