If you receive a message on game launch that ‘mm.exe contains a virus’, this is a false-positive by the anti-virus program and can be ignored. You may want to update your virus definition software which may help, but until the anti-virus software developers update their software you may encounter this message.
There is no virus contained within the MM.exe.
If you are unable to launch the game because of this message, go into your Anti-Virus program and add the MM.exe to your exceptions. If you are unsure how to do this, consult your anti-virus program’s website for detailed instructions.