BIOS Issue for Inspiron 5100

INFORMATION: Dell Inspiron 5100 with Win XP

PROBLEM: Black screen when I turn it on. BIOS screen doesn't come up. I downgraded from BIOS version A32 to A28 using .exe BIOS file because it was heating up all the time, so I used cool pad temporarily. Power light is on and fan is running.

TROUBLESHOOTING DONE:

It tried to reboot and now just a black screen. Power is ON but black screen. I tried to reboot several times using Esc, F1-F12, Del. I tried to move memory to different slot. Tried to remove battery and just run from AC power. I tried to boot using bootable BIOS disc (I5100A32.iso) through CD/DVD player. BIOS screen or Dell logo doesn't come up. I know there is no hardware issue. I tried to remove battery and AC power and then removed built-in button battery (blue) from motherboard for few hours and hold power button for 1 minute. Is it possible to fix it without replacing the motherboard? How do I find BIOS chip and reset it?

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