Sorry about previous post, I'm a little bored here at work so I've gone a bit crazy.
Changing a cpu is simple. There is no soldering involved, infact if there was then there would probably be a lot less computers being built by humans.
I just happened to have my camera at work and seeing as I'm bored I'll do a guide.
Here is a typical socket478 motherboard and cpu with heatsink etc.
You unclip the thingies on the top that lever the heatsink down.
And use a screwdriver to lever off the 4 clips on either side that hold the heatsink on.
Then you just pull the heatsink directly upwards and off. With most socket cpu's, if the seal between the heatsink and cpu is really strong then the cpu will come off with the heatsink and be stuck to it. To lever it off the heatsink, use some kind of strong plastic lever cause anything metal can damage the edge of the cpu and that can kill it.
The one I did, I had already pulled off earlier so the cpu stayed in the socket.
Nowadays all the Intel cpu's are LGA775 so the pin's are actually on the motherboard and the cpu gets held into it with a little metal cover thing like this:
But anyway for this one you just pull the lever up and the cpu can be lifted out with ease.
If you're replacing the chip then you'll probably be using a new heatsink as well and you don't have to worry about re-applying any heat compound but if you are using a 2nd hand cpu and re-using the heatsink. You should always clean off the old heat compound.
I just used a few tissues and rubbed it until it came off.
Apply new heat compound
You don't need much, just a thin layer to cover the top of the cpu without it oozing over the sides. It's just there to fill in the gaps that you can't see and to form a tighter bond between the cpu and the heatsink so the heat transfers as best possible.
The cpu is never perfectly flat, the corners are always lower but as long as the majority of the cpu is covered, especially the very middle which is where all the heat will come from, it will be fine.
Laptop motherboards can have similar sockets, some have levers and some have these little things that you twist with a screwdriver and it allows the cpu to come out.
I happened to have one in my stash of old crap.
All the AMD cpu's still have pins so they're similar to the socket 478.