http://forums.cnet.com/5208-10149_102-0.html?forumID=7&threadID=243885 &messageID=2470487&tag=nl.e497#2470487 Answer: Replacing Windows Vista with Windows XP… Unfortunately you cannot use the system recovery discs from your old computer due to the licensing terms, which stipulate that the copy of Windows XP is forever locked to that specific computer. Even if the old computer is no longer used you are not permitted to install it on another computer, and in most cases technological countermeasures would prevent you from doing so. If you would like to return to Windows XP, you will have to purchase a new copy. Here you have two options: 1.) Purchase a full retail copy of Windows XP, which runs $189.99 from the trusted online retailer Newegg. Certainly not the cheapest route, but it’s a viable solution to your Vista woes and the most accommodative in the long run. 2.) Purchase an OEM copy of Windows XP for around $89.99. OEM copies are far more economical, but they do come with two drawbacks. First, once they are installed you are never permitted to install it on another computer, a parallel of the current situation. Second, you are provided with no technical support from Microsoft. The lack of support in particular should be kept in mind, for if you replace Windows Vista with another operating system your computer manufacturer may refuse to provide assistance should something go wrong. The reasoning is that the computer was designed to run Windows Vista and all other operating systems are not officially supported. That also means that you may be left in the lurch searching for XP-compatible drivers for the new computer’s hardware, since neither Microsoft nor your computer manufacturer will supply them. Thus, either way you decide to go you are facing potential compatibility issues. While XP will most likely present less of a problem, it is an added cost and will result in limited support until you opt to return to Vista. The good news is that we are always here to help, so no matter which option you choose, if there is a particular program or device you are having problems with, we can point you in the right direction.

Because of this I'm sure there are a lot of illegal XP copies out as torrents with plenty of seeds.