My old pc showing no signal
I have a very old pc, few months ago it stopped working for some reason and started showing no signal. Today I opened it, cleaned everything and tried again. I didn't. I thought to use its hdd as an external storage for my laptop, so I unplugged it. Somehow the pc started when I removed the hdd and started it. It shows that I have to select a boot option. Later when I turned it off and plugged the hdd in and started the pc, it showed the same no signal.
Pc specs:
Intel core 2 duo e7500
G31 mobo
No gpu
500 gb hdd
3gb ram
(very old)
I've tried cleaning ram sticks