Hello, and welcome to Tech Spot.
Ok, let’s start from beginning…
It is generally recommended that you list your PC specs with any new thread, so we know what we have to work with. Since you said you do not know much about PC’s you can just list the mode number and we can pull the info ourselves. Do not put just, HP Pavilion or Compaq Presario. That does not tell us much.
First remove all non essential components plugged into your PC, such as: printers, external Hard Drives (HDD), webcams,... So basically all you should have plugged in is Keyboard, Mouse, Monitor ad power cord. Now turn the PC on and see what happens. If nothing happens right away it was recommended that you leave PC running for 15 minutes or so to see what happens.
Q1: So, this is your question one. Did anything different happen after you have unplugged all non essential components and restarted the PC and left it running for 15 minutes?
Q2: Does your PC make any noise (such as clicking noise) or does it beep. If it beeps, how many times?
Q3: Before your PC developed this problem did you notice anything unusual about it? As, did it go unusually slow, or did it make some noises?
Q4: Prior to this incident did you install new software hardware, or did you remove any software or hardware?
Q5: I see that you have access to another functional PC. Is it a desktop or laptop; and what kind?
Please answer all the questions so we can help you better. Depending on your answers there will be more questions after this.