Team Fortress 2 crashes during opening?

I downloaded TF2 after it became free from Steam. The first time I tried to open it, it made it just past the Valve clip in the opening before the screen disappeared. The entire time, the screen for TF2 stayed small and centered in my screen. I've checked the system requirements, possible interference by anti-virus programs, and my game cache. Has anyone else had this problem and, if so, how did they solve it? In case it matters, I have a Dell Inspiron 1420, but Windows 7.