Man, in the future, look up slipstreaming. You can slipstream an original Windows XP disk with SP2 for an automatic SP2 installation during a normal install.
If you had done that, your slipstream disk would be the one not working and you could use your original. Or, just make a 1:1 backup of the CD next time.
To answer your question, TORRENT. It isn't illegal since you'll be using your Windows Key to install which is your license. If you don't like torrent, download an ISO from newsgroups. Not sure what newsgroups are? easynews.com is the service for you.
My point is, you don't need to buy someone's disk with their license. Your license code is still good, all you need is the disk. If you lived near me, I'd make you a copy of my slipstreamed WinXP Pro without hesitation.