Windows Explorer doesn't start?

Hi there ;)

Well, I think I have a somewhat peculiar problem. When I start windows, the welcome screen shows up, then it goes black, my "Documents" folder shows up but then nothing happens. I press Ctrl+Alt+Del and I can see that explorer.exe isn't running. So I ckick Run, type in "explorer" and it starts, along with the rest of the "boot" process, meaning it starts all my programs and etc... So, I have a lazy windows xD

Can anyone guess the problem?