Chris Green - Dude, you have all the info, please put the info here in a step by step guide! BTW - That is a cool thing to do if you are a big DIY computer type like you & me, but newbies blow stuff up, and get hung on simple technicalities.
lukaslevin - When you modify a Mac processor in any way you are asking for non-Mac-type trouble. Buy the new Intel Mini (comes with OSX 10.6) - (what matthewfrey said). I have modified ONE Mac of my 10+, and that was when I put an APPLE Brand PPC upgrade card in my 68000 Mac.
lukaslevin - If you have not maxed out the RAM, then buy more, that is the best way to go, then install MemoryStick so you can tell when you run out of RAM.
http://www.macupdate.com/info.php/id/8069/memorystick
Installing MemoryStick now may help you tell if that is your problem...