BIOS has nothing to do with the formatting process of reinstalling Windows. If you have a Windows DVD and a legible Certificate of Authenticity on the base of the laptop showing the Product Key, that's all you need.
Just put the disk in and press whichever key you need to boot from the optical disk and Windows will format the old system out of existence. It should also offer you some repair options which will save you losing all your personal files and any installed programmes you put in.