Won't enter my computer

Hey, i've got this problem with Windows 7. i've installed it yesterday, played a little bit around, and a few hours ago, i was trying to change the themes, but the windows wouldn't show up. it wouldn't start, and i can't figure out why. so i've restarted the pc, but after that not even the explorer window worked. sorry for my twisted words, english is not my strong point, and it seems windows 7 isn't either.

So now, i can't start any explorer window, or preference window, surprisingly, control panel works, but from there, i can only open keyboard and mouse settings. I don't know what to do. it would be nice if you could help me somehow.

Insert boot medium, choose Repair Install.

Can you try booting into safe mode (F8 while booting). If you are able to and it looks normal this may be nothing more than a video driver.

Let us know

as it turns out, the theme engine was the problem, because all i had to do was to open task manager, goot thing that worked, and closed the theme service. but thanks for the feedback.