You should be able to enter the BIOS during the boot process by pressing a particular key - Del, F2, F10... Which key depends on the manufacturer. Reboot the PC and watch the screen when the manufacturers logo screen appears. It may require a couple of reboots to catch the text that says which key to press. Once you know, reboot and start pressing the key repeatedly. PCs boot faster and faster, and the window of time you have to hit the key has gotten pretty short.