I also want a bike, I fear I'm destroying my knees by running.
To follow on from that post above.
Running definitely messes up your joints in the long run - you're slamming a good few times your weight on the hard ground each time you take a step. Fluid movements like biking are much better for them.
Use a bike/exercise bike over running if you can.
(bonus points for knowing it!)
Some sort of CAD isn't it?
All I see is a sweet Tony Hawks level