There are so many prior answers (google The Dead PC) that you may be hoping for less answers rather than so many.
You left out make, model so my answer may be vague or wrong.
Try booting some Live OS like I noted a few years ago at http://tips.oncomputers.info/archives2004/0401/2004-Jan-11.htm
That way you can look around to see if the HDD is gone, missing, etc.
Want to ask.
I have a problem, when i turn on the pc, beep sound not normal as usual, then after beep, scanning bios until loading windows does not appear only blank / black screen, but not long screen enter login page windows as usual.
Video: https://youtu.be/T4u6u8RCRcc
RAM is checked, and all looks normal except that earlier ..

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