I just got a T-Mobile Razr from work and need to change it to work for ATT.

in order to do a seem edit, you should read (but not necessarily do) the seem edit guide to get the general idea of how to perform a seem edit. I also suggest you to post a forum topic of this issue so that we can firstly get your phone connected to the computer properly. You need to have the phone recognized first before you can proceed further. When you post your forum topic, please be as concise as possible stating which drivers you installed and how you did it.