To install Forefront Client Security manually with the options for the client machine to contact the MOM Server (managed), run the below command:
Browse to the folder within command prompt to where clientsetup.exe resides.
Type the following – clientsetup.exe /CG ForefrontClientSecurity /MS MOMServerName and press enter
In most cases /CG is ForefrontClientSecurity but may be different depending on what you originally set it to.
To install without MOM so the client is unmanaged, type clientsetup.exe /nomom