My computer boots up and like 30 seconds in to the boot it will freeze?

my computer boots up and like 30 seconds in to the boot it will freeze and wont boot anymore and beep 3 times and med speed so i got a new mobo and video card and swaped the cpu and ram and still does it so now i have a new mobo and video card and same problem now i am down to ram or cpu or psu and i dont want to buy all 3 and ind out my cpu and psu was fine what do you think it is. like ill turn it on i can go to bios i can move the cursor up and down in bios after about 30 seconds it freezes and wont boot any more for like an hour