Hi freptide,
This website has an excellent "Build Your Own PC" tutorial that you might want to go over:
http://www.pcmech.com/byopc/index.htm
There's a section on hard drive preparation that should help to explain what you have to do in order to get the hard drive ready for the OS:
http://www.pcmech.com/byopc/step/24/
And here's the section on installing the OS:
http://www.pcmech.com/byopc/step/26/

Cricket