Go to the link I provided in my last post. It tells you how to access the BIOS.
A computer can boot from a hard drive, a floppy drive, a CD drive, and, if the BIOS allows it, a USB device. Like many computers, your computer is apparently set to look for the hard drive first when booting. You need to access the BIOS and change that. Then, once you've formatted your hard drive and reinstalled Windows, you can set hard drive back to initial boot device.