How do I make a mountain bike go faster (commuting) I just began biking around 4 months ago, and due to lack of experience I bought a Diadora Orbita Mountain Bike. I've staring commuting to work recently (about 14 km daily) but I'm not exactly happy with my speed (around 17 kmph with no traffic) that is after inflating my tire and cleaning the chains on regular basis... Would changing the tires into thinner ones make my any bike faster? Are there any other modifications that I can apply to my bike to make it go faster? Or would be easier to just buy a road bike instead?

 (generic image)
I started commuting the same way about 8 months ago on a 29'er mountain bike, 2 things made the trip faster and more enjoyable.

Firstly tyres, I changed from knobblies to slicks and it made a BIG difference both in feel and actual speed.

Secondly I got a lot stronger from biking every day.

I eventually got a lighter cheap touring bike which is faster, and better in many ways, but I still prefer the mountain bike for fun.