Pc won't turn on. PLZ help!?

I started downloading a pretty big file off of the Internet ( 7 GIGS ) and then I left my house to go see a movie and get some dinner. It was about 6 hours before I got home. When I got home my PC was on the Dell boot up screen and was not making any progress. So I unplugged it plugged it back in unplugged all the extensions restarted it and everything, and it still won't boot up. Will some one please help me. Its a PC running Windows 7 by the way.