Good advice above. 3 more things to keep in mind:
#1-since you are on Windows, go into Settings>Sound and make sure that your interface is NOT the Windows Playback Device. Set that to the computer's sound card(likely "Realtek"). The reason for this is that windows likes to take control of the interface and lock Pro Tools out of setting the sample rate(you may need to check and reset this after a Windows update).
#2-The term "sound card" usually refers to the on-board sound of the computer. Your external box(the Fast Track) is an "interface"
#3-If you are going to leave your computer on, but leaving for any length of time, Close Pro Tools. The reason is that Pro Tools just doesn't like sitting idle for hours on end(at least not for me). And, if you lose power while a session is open, its possible that PT is in the process of saving a backup(assuming you have auto-backup enabled), the data could be corrupted.
