pc wont boot


Nov 12, 2017
I bought a pc for my dad its a single core 3.0 that have 2500 intel hd integrated graphic.My problem is when i bought it i instaled a fresh windows xp os and it worked fine,instaled antivirus chrome everything was fine.So i disconected the pc and put it in corner of my room.Fast foward like 2 mounts i find a ddr 3 stick that i know its from that pc and i stick it in but i did not try to power the pc cos i was bored to connect it to my monitor and everything so i let it like that.Fast foward from that 6 mounts i bought a monitor for that pc and keyboard/mouse speakers and decided to complete the build,put inside windows 7 cos my father want it to be in native language and there problem starts.When i boot up pc it goes into loop of 5 sec,he starts the vent of cpu and after 5 sec it restarts and it goes into loop like that.I try to re-seat ram,i try only one slot,i try to remove the ram to see will i have beep sound and i got it,I try to remove the bios battery still nothing,i try the re-seating the cables to see maybe some cable is loose.And yet same problem.So do you know how can i fix this prob?