The first and most important thing about bike commuting is that it's easy as riding a bike, so get out there and try it. You can read a lot of stuff on the Internet and research yourself into a corner trying to figure out exactly the right bike and equipment and strategy, but all that is icing on the cake. You will very quickly figure out what you like or not and what you need to do.

This was a very inexpensive bike to begin with (~$230 new in 2004, about as cheap as they come from a bike store). It's from a good brand, so you can at least be sure it was built well and will work. It will have all the holes you need to mount racks or fenders if you want them. Inexpensive mountain bikes like this make decent commuters, they are comfortable and tough and you can always find a low or high enough gear. It's not going to be light or fast.

Get some lights.

Right now is an excellent time to shop for deals on 2014 closeout bikes. If you can find an REI or a Performance Bike in your area they won't lead you wrong and they tend to be less expensive than say Trek or Specialized.