ok so its probably either keyboard,most systems will boot with kb unplugged,ram..again systems usually start with only one card in or cpu,sometimes reseting cmos on motherboard cures this..there should be two pins near mboard battery remove power from mains and remove battery then bridge with jumper or screwdriver rst cmos pins refit battery whilst still bridging ,then remove bridge and power up,you will probably need to reset bios time after this and any options may revert to default in bios,just press del. after post beep to enter bios and make changes f10 to save and exit,one of these should work but start with easiest and work up