To try to get into the BIOS, you should unplug all devices that are not needed (Hard drives, CD-Roms, network cards, sound cards) and see if it will let you in without freezing. If that doesn’t work, then you can try to clear your CMOS memory. WARNING - If your bios is corrupt then this could prevent your system from booting at all, and you might have to buy a new BIOS chip or motherboard. Or you could hot swap the BIOS chips, but that’s another story..... If you want to try to clear the CMOS, read on....
To do this, you have to unplug your computer and find the necessary jumper on your motherboard. Change the jumper to "Clear CMOS" for a period of ~1min, then change it back to normal and plug your computer back in. If it works, then the computer should load the BIOS defaults and allow you to edit the Bios... if it doesn’t work and the BIOS is corrupt, then you are out of luck... Try this at your own risk. Good luck

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