Here's the google for this one. I'll summarize what we do with dead PCs after that.
https://www.google.com/search?q=How+to+repair+The+Dead+PC
In short you use content like that to try what you think it is this time. There is no exact do this for all dead PCs but I tend to first look at the machine inside and out then bring out my Volt meter to check the CMOS battery and power supply levels.
FULL STOP. There are basic tools and skills to being a PC tech. Some try to avoid having the Volt meter and use thereof and those folk tend to replace parts over diagnosis. That's OK. It can get the job done.
Hi, i have an old desktop pc when i turn it on i hear the fan work then it just start peeping and nothing appear on the screen, i don't know where is the problem? sombody help please?

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