Last year I purchased an '06 Trek 4900 mountain bike. At the time I purchased it in the hopes of getting into some trail riding that next summer. Unfortunately due to an injury my days of off-road mountain biking are pretty much over. So now I have this 4900 that's barely been used sitting in my garage. With gas prices on the rise, I've decided to try riding my bike to work and grad school over the summer. I know the 4900 was not meant to be a commuter bike, but I was wondering what all I could change on the bike to possibly turn it into one. The obvious first thing would be some new tires, ones that were more road ready. Anyone have any suggestions? Also, is there anything else I should look into to adding/changing? I'm not too concerned about having any kind of rack on the bike, as I'll be carrying a backpack with me that can hold all that I need.

Thanks in advance to anyone who offers advice.

P.S. Here's a link to my bike. Click Here!