Manage.bde.exe (or other command) is not recognized as an internal or external command

When you are trying to use a 32 bit application and that application is trying to execute an action that calls a feature from System32 (on a 64bit system) you have to use a specific path.

Use the following path in your batch file:

%windir%\sysnative\application

 

Example

So, to enable Bitlocker on C: drive

%windir%\sysnative\Manage-BDE.exe -on c: