Cpu won't pass the bios booting.

Hello, I don't know if I'm gonna get any help, my CPU for my desktop fires up properly fans run and slow down it won't (CPU) pass the bios stage, just freezes. Shows Hp invent and F9 reboot F10 setup F11 e.t.c and just sticks there no keyboard response mouse turns on. Well infact this happened when I changed my CPU casing. I don't know whether I disturbed some connections or something. I first thought ram was the problem so I changed it still nothing happened then changed the processor nothing happened Hard drives' proper, I've just run out of ideas. I can change the cpu but I'm in love with this one. I just don't know what to do.