Updating Bios

Hey how's everybody out there, my ? is how to update Bios. I'm not and expert, but I'm new to this, I recently upgraded my PC, I have and ASUS P5N-E Motherboard, and the CPU used 2 b and Intel Core 2 Duo. In my rebuild, I kept the same motherboard, but upgraded to and Intel Quad Core, EVGA GeForce 9800GT, 4 Gigs of Ram (Corsair), Sata HD WD 640GB, Sata Optical Drive (Plextor), Zallman heatsink, all in an Antec 900 case. Upgrade went well, everything is running fine, I'm running Windows XP and that's also no problem, but when I turn on my PC I get this message b4 I get 2 Windows " Unknown CPU detected . Bios update is required to unleash its full power" How dod I do the update, and is there a simple way, cause I heard it could get very tricky. Can I do the update with a thumb drive, or is Floppy the only way 2 go? Help please, if anyone knows, ur comments r gr8tly appreciated. Take care.