PC build won't start.

[Wainuitech]

As it was suggested before, try starting the board outside the case.

All you need is the motherboard on a bench, with CPU and Memory installed attach ONLY the basics, PSU, Keyboard, Mouse, and monitor -- You don't even need an HDD. You can start the PC by shorting with a screwdriver the + & - on the pwr pins. Its very rare for CPU's to cause a problem.

When it's out of the case as described, and IF it boots into the BIOS and stays there - the problem is possible somewhere there's a short. If it boots, then turn it off, add one thing at a time ( HDD) try again see what happens or if one particular item causes it to fail.

If its still not booting, good chance it is the motherboard

Actually had that happen several years ago, Built a brand new PC there was "Something" about the case, when it got bumped it wouldn't start, or would then shut down within a few minutes, went through and changed Every single component, wasn't till the case was changed the problem disappeared -- (Had spare parts then)