Dude, if I were you - I'd take it to whoever you bought it from.
If that doesn't work, maybe try reinstalling windows - if you don't have the disk, try Ubuntu.
It's Linux, and that means free!
Anyway, if you don't like Ubuntu, there's a whole slew of other open source OSs - go to this site
for ideas - try the "Major Distributions" or "Search" options at the top.