Windows wont start unless I unplug and replug AC cord

Registration date
Tuesday February 9, 2016
Last seen
February 9, 2016
Hello, Ive got problem with my PC. When I start my PC windows wont start and I get stuck at HP logo. My keyboard wont work so I cant even access BIOS. But when I unplug and then re-plug AC cord PC starts normally. Happened already twice.

PC: it is HP Pavilion Elite HPE-h9-1000cs Phoenix
but year ago I have added SSD disc Kingston HyperX 3K SSD 480GB and I changed original RAMs so I have 16 GB of ram.