It's all here.
-To get to the computer's Basic In/Out System (BIOS):
Rapidy tap a key as you turn the computer on. The key is usually "delete", but if that one doesn't work, try the others posted above.
-Once your in the BIOS, you'll see some tabs and a lot of terms and settings but, just use the arrow key to scroll over the the "boot" tab.
-Then arrow down to highlight " boot priority" or "boot settings" (<--something like that). Select "1st boot device" > <enter>. There will be options. Select [your cd/dvd drive] and press ENTER to make it 1st.
-Insert the Windows 7 DVD.
-Then ESC key, go to EXIT tab, select "exit and save settings" > <enter>. The computer will reboot to the DVD.
-Follow the steps, and when you get to "Where do you want to install Windows?", select "Drive Options (advanced)".
Pics
-Follow the steps to delete partitions, format the HDD, and select "where to install windows". The installer will continue so finish its steps and your done.