At 6 years you should be on the second or third battery. If not that, try a new or working motherboard.
BE SURE TO STRIP THE MACHINE OF ALL DRIVES. You don't need them for a video bios display.
My Desktop ( LENOVO TINKCENTER A29) since 6 years i m using it.
Computer start when i press Power Button.
Keyboard LED once blink and goes away.
Mouse power is on.
Processor fan and SMPS Works.
But Does not shows Display and Bios MENU
Step taken to solve the problem
RAM Properly Fitted . EVEN I CHECK the RAM on another MOTHERBOARD the RAM is TOTALLY Working.
VGA CABLE was also check even my LCD to on my another Board The VGA and LCD also Working.
The VGA port is also ok.
I re-assemble the Machine to but not work
one of My friend told me about BIOS Jumper but check it out I remove the JUMPER and INSERT again ; nothing work.
I don't know why what happen
It is Second TIME happen. First time I have to Motherboard Repair He solve it out but never told me have happen.
I Know the Motherboard is GOOD even RAM and Processor.
Pressing the POWER ON Button
Slight blink of LED and goes away.
internal MACHINE working even hardDISK working
I think it is Bios / Motherboard problem
What you say