My Computer has a big problem and also its a custom built pc and its always black screen nothing shows this happens in the vid

Solution
Seems to me your PSU may be the culprit. That beeping sounds like a voltage drop warning to me. Change the PSU and check it out. You may have damaged the GPU through under voltage as well so try swapping that out after the PSU swap.
Seems to me your PSU may be the culprit. That beeping sounds like a voltage drop warning to me. Change the PSU and check it out. You may have damaged the GPU through under voltage as well so try swapping that out after the PSU swap.
 
Solution