You should consider a complete dissassembly of your pc and to plug everything back in. Also make sure everything is plugged in correctly. If you don't feel to do it, just unplug the basics components leaving only 1 stick of ram, hdd, mouse keyboard and your screen plugged on the integrated graphics. If that works, start plugging everything back in.
That could be a power supply issue too so if you could write your config here i could see if that's about it.