First off, welcome to webmasterworld.
Well, as for putting a laptop processor into a PC motherboard... I don't think it will work. From what I've seen, the Intel P4 M (for example) supports 3 different voltage inputs... Regular, low and ultra low. They also come in different sizes... 130nm and 90nm. I think that if you try to use a laptop processor in a PC motherboard, you will fry either, or both.
Here's an idea though... you can sell parts of your laptop on somewhere like ebay and probably recover enough money to get a real processor. I've seen LCD screens go for $150 and up if it's a new model. Also, you could scrub the HDD and sell it too. PC HDDs are so cheap now that you could probably sell your laptop drive for more than a PC HDD. (I just bought a 200gig WD for $89.00 US)
So, if I were you, I would part out the laptop and start building with the money from it.
PS... if anyone knows for sure if there is a differance in voltage between laptop and desktop processors, I'd also like to know.