Hard Drive Failure

So my computer will not start up! It is a custom built computer which is over a year old and I have never had any problems with it till now. One day I turned my computer off to clean the dust in the case and when I go to start the computer I get to the loading screen (the screen where it loads windows) and nothing happens! It just stays there. I can hear that my hard drive is starting up and it sounds normal.
The only thing that I have done to try and fix this is put the Vista CD in and tried to fix from there but it don’t work. I really have no ideas as to what is wrong.
Can someone please help?

I never broke anything on the mother board or any other part.

did u reinstall vista or do the fix thing… try safe boot and system restore.  Vistas always been good to me about factory restoring