hey all i really need some help, i was attempting to edit my bios settings so that my computer would recognize the windows XP disc i had in the drive as i wanted to format my computer

i basically changed it to what i believe was making the cd-rom drive the priority drive to boot up from on loading (or something similar), im guessing this was a bad idea as when i saved the settings the computer screen went blank and the computer started sounding a siren type of sound, i pressed the restart button on the actual computer but nothing happened. The siren continued and i had to turn of the actual mains power socket to stop it! Now the computer WONT TURN ON AT ALL!

ANY HELP WOULD BE REALLY APPRECIATED AS I AM PRITTY CONCERNED AND HAVE NO IDEA WHAT TO DO

Regards
Chris