Re: Little help - dead Mobo or CPU...?
Maybe there's a problem with the current, but I wouldn't start to tinker with that. It's weird that it doesn't do anything at all. A friend of mine had MOBO problems once, but the "light" of the start up button still worked. I wouldn't know about the CPU though. At most, I'd try to switch the cable, see if the box is just without juice or something. No lights usually mean no power.
Don't put stuff from a broken computer into a working one unless you're absolutely sure the damage it might cause won't go beyond repair.