building a computer from old parts
I wanted to buy a new computer but the cost is sort of prohibitive. My school has a lot of old computers lying around from the early 2000s, and I was wondering how much trouble it would be to cannibalize parts from several of them into a decent computer. How much prospect is there in such an attempt? I don't really know very much about building a computer, but I believe you can combine processors in parallel for a more powerful processor? I assume I would at least have to buy a new mother board which could be expensive, so is there a workaround to that? I'm not even sure what kind of condition they are in, but I wrote down some of the models anyways, and there are multiples of some types
Precision 530 with Intel Xeon
SMM Power Edge 230 Intel 3
DHM Intel 3
Inspiron 8500 Intel 4
Power Mac G4
Silicon Graphics 320
The Inspirons are laptops, so would I even be able to salvage parts from them? Aren't their parts usually integrated into the motherboard?
I am currently using a Toshiba Satellite A215, and obviously I would want to be able to build a computer more powerful than it, otherwise I would just be wasting my time.
Since the Graphics cards are from the early 2000s, would I need new ones if, for example, I wanted to run a newer game? Is there any use in saving them?
I did a little research on some of these models myself, but I don't really know what was important to post on here, so I was hoping someone could help me research them and tell me about which to start with. Am I correct in believing the Intel Precision 530 is the best right now? Is there any way to cheaply salvage any of this into a workable, decent computer? If it is possible to build a better computer than my Satellite laptop using these old computers, how much trouble/cost can I expect it to be to be compared to the benefit or compared to just buying a new computer? I expect to have to replace some things, but hopefully not much. Also, since I am kind of experienced with this type of thing where is a good resource to learn about computer building?
Thanks for any help.