I had issues when it came to getting both Medieval 2 Total War and Shogun 2 Total War to start on my PC. I downloaded both off Steam and neither one would launch at all. I actually reinstalled M2 twice, thinking the problem was the game. The preparing to launch screen would simply appear, then disappear and nothing would happen for both M2 and S2, until...

I installed the .NET Framework from Microsoft.com

Framework 1.1, 2.0, 3.5 and 3.5 SP1 are needed.

If your game refuses to launch without error, the problem may be a lack of the Framework.

All 4 are small downloads.