Argh...more problems...thankfully not mine...

One of my friends bought a DVD burner today and wanted me to install it for him so I was at his house, got it put in, hooked up and everything and turns out that his old CD player/burner never worked so I figured good luck trying to get either to work. I thought it was his motherboard maybe? I don't know but I tried just throwing his hard drive in an old computer of mine that I knew the motherboard was good in, it was a P4 with XP, now why won't his work in it, his is XP too.

Here's specs of his:

2.53 Celeron, XP, had 254 ram,

And the one I had was:

not sure what but a P4, XP and had same ram.

So I took the hard drive and cd drives out of his, along with the other ram card because it was the same type and hooked it all into my case. Now It is detecting all drives but It won't start up completely. It gets to the point where if you shut it off manually, it'll start back up with the choices of start up method. Can I not do this?? They're nearly the same motherboard's too, look the same. It's just the one has a 478 pin which is what, not quite an inch square, and my old one has a big ass one that's prolly 2 inches square, along with more slots for video cards and such.

Is it not possible just to drop his hard drive in it and have it run, is it something with the processors? Please help me on this as I'm damn near dumbfounded and he keeps trying to tell me it's the wiring, it's not because I know everything is working.

I'm just wondering if he has formatted his drives with password entry?