If you want to reformat his hard drive under Windows 7, because he has captured, for example, the Federal Trojans as malware, which must proceed as follows to do this:
Insert your Windows 7 installation CD / DVD into your drive and restart your PC.
Either the PC will start automatically from the Windows 7 CD or you need to set manually in BIOS to boot from CD / DVD.
To enter the BIOS, press during startup the F12 key (This is different for every BIOS but is usually displayed at the bottom of the screen) and enter the BIOS.
There select the "First Boot Device" the CD or DVD from the drive. Save the settings and exit the BIOS. The PC will restart again.
Now the Windows 7 DVD loaded and some instructions appear on the screen. Among other things, the terms and conditions. Do you agree with this in order to continue the process.
Now you will be able to see the various disks and partitions on your PC. Click on the button "Advanced Options".
In the following settings you can reformat the hard disk and partition equal to new, if desired.