BOOT UP PROBLEMS

Hello,
THERE IS THIS COMPAQ DESKTOP PC WHICH I HAVE TRIED TO BOOT TO NO AVAIL.IE IT BOOTS AND DISPLAYS ONLY THE COMPAQ SCREEN W THE FOLLOWING:F10 FOR SETUP AND F12 FOR NETWORK SYSTEM BOOT.WHEN I HIT EITHER F10 OR F12 KEYS,IT DOESN'T RESPOND.I HAVE ALSO TRIED TO REPAIR THE INSTALLATION WITH THE SAME OS AS THE PREVIOUS ONE BUT IT DOESN'T BOOT FROM THE CD-ROM.I HAVE ALSO GONE FURTHER TO CLEAR THE CMOS BY REMOVING THE BATTERY AND RE-INSTALLING, BUT THERE IS STILL NO RESPONSE.PLEASE HELP ME I'M CONFUSE AT THIS POINT AND DOESN'T KNOW WHERE TO CONTINUE WITH THE NEXT TROUBLE SHOOTING PROCEDURES.