Windows 7: PC boots sometimes, but is mostly starting up then switching back off

Good evening everyone,

I built a PC for my cousin a while ago (well more like a few weeks) and from the very begining it was screwing with me by not being able to boot to a screen, fans would just start up then power down after 10 seconds or so. It use to uncommon but now it does it all the time.

What i tried:

1. Reseating and cleaning of wires ram etc. (basically rebuilding everything again apart from the CPU)
2. Reflashing the bios to the latest revision (if i manage to even get in)

What i request:

1. I just want some basic tips or however complicated on troubleshooting or maybe even your opinion about the situation. I will supply a list of parts after this section

Parts used:




Many thanks for anyones help