While you may have seen instructables that say "free" but you still have to pay for materials/suchlike I will start off by saying that the computer i got costed absolutely zero and i got it in less than 1 day. The monitor was also free as it was "incompatible" pah silly people it was just old.
The only downside is that it wont be brilliant, at best it will be a spare/homework computer so dont be looking to replace your sick alienware gaming computer that you overclocked so far it caught fire.
Step 1: Problems
Believe me not many people will throw out a computer that has NOTHING wrong with it. Though dont lose hope as the less computer-literate will take a dying hard drive as a dying motherboard and decide that the computer is old enough to justify throwing out instead of taking to an expert. This means that your computer won't be made of one but of multiple broken computers. This can also make it better by getting the best of everything.
Step 2: Different Methods
Methods of getting a new computer are varied and will depend on where you live.
If you live in an area that does council waste pickup then brilliant! Go to the next step
If you live in an area with lots of dumpsters, or just a few good ones, go to the step after that.
If you have neither of these then the step after that, or
If you live on the moon go home
Pictures are stuff i collected, not alll of it though
Step 3: Council Cleanup
This is the best way of getting a new computer short of getting one your university/college/whatever is throwing out. With everyones year-collected household waste spilled out into the street you merely have to walk around a few blocks, (I rode but still) and you are bound to find plenty. This is the way i found mine.
Step 4: Dumpster-Diving
Well you all know what to do here dont you. And if i say the wrong thing about Americans and dumpsters I'll have a hundred angry commenter bees stinging my eyes before i can say, "I didnt mean YOU were the trash." So ill leave dumpster diving to you and a link.
This one has good info.
Step 5: Hand-Me-Downs
For this one you will need to know someone or a company that is throwing one out.
Step 1. Ask politely
Results: new computer
If its a company they've probably just chucked it in a skip/tip, just hoist it out and there you go.
Step 6: Putting It All Together
Check the computers to see which one works best. I had one running xp and one running 98. Guess which one i went with.
Only problem was it only had 15gig! Luckily i had found a 40 gig hard drive that worked in it and i ran that.
A missing CD drive was replaced and everything put back together.
Step 7: Done
And there you have it. your very own FREE computer.