Make sure you have the latest drivers for the Fast Track and your operating system. You can find them at the M-Audio web site.
Once the drivers are installed, open SONAR, go to Options>Audio and click the Wave Profiler button, or check if ASIO drivers are aleady listed under Driver Mode. If ASIO is there, go ahead and select ASIO.
Then make sure that the FT is selected as both Recording and Playback Timing Masters and that it's Drivers are selected
What kind of microphone will you be using? What's your operating System? What speakers are you using (laptop speakers or speakers connected the the Fast Track)? You should use the FT for both recording and playback and not the stock computer sound card.
You may have to go through all the tracks in your old projects and set the outputs to the Fast Track if they are not already selected.