PC goes into a continuous boot loop?

[__Jpike]

So my cousins pc has just started going into a continuous boot loop, where the motherboard logo wont even show up and he cant seem to enter the BIOS. Events leading up to this stage: I sold him the pc without a PSU and with an older Hard drive with windows installed. He has been playing video games and browsing the web and just everyday things the past week without hitch when this problem suddenly occurred two nights account. 

Trouble shooting done: Put in a different hard drive with windows already installed, tested the PSU with the paper clip method and it "appeared" to turn on, and lastly we reseated the Ram and Gpu.

 

If you have any solutions or resolve to our problem it would greatly be appreciated.

[paddy-stone]

Reset CMOS and try booting again.

[__Jpike]

22 minutes ago, paddy-stone said:

Reset CMOS and try booting again.

We have already tried that, I forgot to list it