Execution files infected

Hello,
I attempted to run a video file off the internet. I got a text box asking if I wanted to save or run the file. Without thinking and simply closing the text box, I foolishly clicked on run. This file proceeded to infect the execution files on my computer while bringing up a screen telling me my computer was infected and offering a virus scanner from some unrecognized company. I did not go for that--assuming it would request a credit card number and leave me in even bigger trouble.

The problem is I can't use my computer. It continues to bring up the virus warning and virus scanner offer. I can't use Explorer--I get a message that it is corrupted. Task Manager gives me the same message that it can't open because it is corrupted. I tried my computer's virus scanner and it stops dead at 31 percent.

I need help. Can you offer a solution.