What OS (vesion of Windows) are you running? How old is your computer? You said in your original post that "we just rebooted my computer about a month ago because we had a lot of viruses". Rebooting simply means restarting your computer. That's not what you meant to say, is it? Did you mean to say you formatted your hard drive, erasing everything on it, and then did a fresh installation of Windows?
Do you know how to open Windows Device Manager? Have you looked at it since you did whatever you did about a month ago? Specifically, does Device Manager indicate your Display adapter is working properly? What is your Display adapter, i.e. the name of it?
Can you run dxdiag? To do that, go to Start, Run, and enter dxdiag in the Run box. When the DirectX Diagnostic Tool appears, click on the Display tab, and then click on the button for Test DirectDraw. Did the test report "All tests were successful."? Is DirectDraw enabled?
Can you use animated screen savers?