Downloading a free copy of this program is highly illegal. IT violates copyright lawas. even if you get a copy you still need a key to access the program or it won't work.
Well, technically that's illegal, but making a quick search on google for "torrents" of it should yield many results. Beware, though. If you get caught it's a big penalty.
There is no legal way to download Windows XP Home Edition for free. You might try a torrent or even just your standard search engine. If you can get a "crack" for a key code all you would need is to borrow the CDs from your friends and then you're all set.