If it's a shop bought PC the beep codes may be on a label on the inside of the case. If not then you can search by BIOS make, ie Phoenix etc, on Google or whatever.

But most often it'll be poorly seated/dirty connections, of RAM, video card etc. Best bet open the case, take the RAM and all cards out, blow away dust, reseat them and boot up again.

Oh and from your first post it could even be a keyboard problem, someone spill tea on it and not tell you perhaps?