Installed Blender on a machine with Core i7 CPU, 16GBs of RAM and an NVIDIA GeForce 650. I managed to run Blender twice. On the third time nothing was shown and Blender didn't load properly, even though the active icon is in the tray and the program is in the running application list of task manager. Why is this happening?
Do you usually work on two screens? (Two monitors or a monitor and a laptop). I have found that if I use Blender on the second monitor and then unplug it, Blender will not automatically come over onto the primary screen.
You might need to plug in your second monitor, (if you have one) and see if it is there.