I weight train 5 nights a week and run for 20 mins each time at a good pace.

Is this an ok balance of CV and weights?

I want to reduce the beer belly so I run everytime but I don't want to reduce muscle aswell. How long before I start seeing some results?

Hey, I think that's a pretty good combination, as long as you are doing the weights and eating healthfully, you don't need to worry about losing muscle. If you've only just started results probably won't show for a while, but be patient. They will!
--Sis

I think 5 nights of cardio is excessive. When it comes to fat loss, all you need is 3 days of interval running and/or sprinting at 15-20 minutes each session.