I like the post with the video link showing Linus Torvalds; it is important to NOT buy a computer with windows on it; if you have to, buy a used one, though techinically that supports the previous owner's proclivity to purchase windows computers, so NO... lol
if you really want to be serious there are a few options
1. find a manufacturer that sells new computers/laptops with Linux or NO operating system at all (the windows license is like $3 for the oem, but it is the principle that matters!)
2. buy a used (or refurbished) computer with linux or NO operating system at all (ebay has vendors selling systems pre-loaded with linux)
3. make your own; there are laptop barebones kits you can buy; not cheap, though; you get the basics, you install your own hdd, memory, maybe even processor
4. last resort: any laptop with windows is easily reformatted by linux, even saving original windows in smaller partition (shrinkage)
you are better off buying a new or refurbished laptop; the value of older laptops does not match their price
here is a quick price scan for cheap laptop on newegg.com, just for fun:
http://www.newegg.com/Product/Product.a ... 6834200627price is $159
... really, you would rather pay 2x for a better computer than have 2 of these, so save your money, or maybe not, lol; i could see giving two to children, say 10-15 years old? this computer will barely play facebook games, but it will, lol
oh, wait, this is for linux, well, same difference i suppose ;]