Booting/Blackscreen problems

[utopianexile]

So i got this second hand computer off the internet (completely cleaned) and everything has been working fine the last few weeks. i even upgraded the graphics card and installed a ssd as a boot drive with a new download of windows 10 pro on it. took some time to learn to do it properly but went off without a hitch...for the most part. after downloading all the necessary drivers and, wanted programs, and linking all my accounts from previous computers; i started to hit some snags. i started having problems with loading games off steam and for the most part had fixed the problem. the biggest problem that i have noticed is the if i install any programs that require a system restart or reboot it took its merry time doing so. i am trying to learn how to video edit some of my streams from gaming, so i downloaded davinci resolve(the free version) about 36ish hours ago. it required a restart and that brings me here, my computer has not booted back up despite the hearing the fans going and the ethernet hub indicating that there is information transfer, the screen doesnt register that the hdmi is plugged in either so i cant tell if it is actually off or on. im confused and not sure what has caused this or pushed the computer over the edge. im relatively new to building and understanding computers so im not sure if i pulled a rookie mistake or what. so yeah please help and thank you. oh and  specs below if necessary for help.

 

HP Elite 350t

750gb hitachi hdd original

pny 120gb ssd  new

intel i7-860 @2.8ghz original

xfx radeon rx550 4gb new

power spec 550w 80+ bronze new 

8gb ram installed 

windows 10 pro new 

lg 24mp59ht 75hz new 

i think that is everything, if you need more you need only ask