Normally if the Maya startup doesn't work you will get 2 windows - 1) the Output Window, the 2nd being the script editor. In the script editor there would probably be some Mel startup error, which would give a good indication of what is the problem. When Maya is starting up it outputs in the slash screen what step it is along the way. knowing what the last step output can also give a clue as to what Maya is attempting to do.
A couple of common reasons for this would be:
1) the user prefs are corrupted or setup for a different version of Maya
2) the graphic driver used is not providing the required OpenGL contexts that Maya wants to use.
for 1) rename your user prefs directory and let Maya ask to create default prefs
for 2) using Microsoft's drivers are not sufficient (OpenGL 1.0/1.1 only) install the ATI/Nvidia drivers from their web site. For the consumer cards you may need to try a couple of driver versions to find one that behaves reasonably
Wayne Arnold
Developer