Unable to reinstall Windows 7 Home Premium to clean the Computer

Hi all

I think I'll go crazy i some minutes...
The computer of my parents is full with several viruses. So the easiest way to clean the comouter is, to make a new setup and rei stall Windows.

So I inserted the original Windows 7 install DVD, and set the DVD to the first position in BIOS. But when it starts from the DVD, there is only a black screen with a small "ED" on the right bottom of the screen. And that for minutes! Wtf??

So istarted the old to replace Windows and started it over the explorer. This works. But when I came to the screen where I can chose the partition, i'm unable to format the hard disk, because of missing drivers. Where is this?
So i installed it on a other free partition and it worked. But i keep having all the trash on the hard disk. So i tried to format the partition over the explorer. But it dont work.

So please help me, im going crazy! How can i reinstall this??

I've Windows 7 Ho e Premium x86

Thanks

Try Cleaning the HD Drive first, using Step one in this tutorial:
SSD / HDD : Optimize for Windows Reinstallation