If you know, please tell me how to format the hard drive so I can do a clean install of windows 7.
Basically the same way you format prior to any other installation..... just be sure there is nothing on the drive that you want to keep.
Boot from the installation media
When the pick your language and keyboard layout screen comes up, hold the shift key and hit F10 on your keyboard
In the dos prompt window that is produce type
diskpart
hit enter
At the DISKPART> prompt type
list disk
hit enter
Now the most critical important part of the process
Determine which disk you want to work with..... ideally there should be only one, just make sure you do not choose the wrong one, when you type
select disk 0 (
where 0 is the disk you want to work with)
hit enter and type
clean
hit enter
type
exit
hit enter
type
exit again
hit enter
Proceed with the install, that will auto configure the disk or if you want create and size a partition for installation, although I would generally recommend accepting the defaults and doing an sizing or resizing afterwards.