We're (at least I'm) not trying to be rude, but a search on google provides 205,000 results:
http://www.google.com/search?sourcei...io+unlock+code
A model number may help narrow these results down a little bit. (KDC-MP522 provides only 10 results.)
http://www.google.com/search?hl=en&s...22+unlock+code
Here's kenwood's contact info from their website, there's a shiny 800 number and everything. If you're a little more anti-social, you can select car and home from the drop down box and fill in the information there, and someone will e-mail you about it. Assuming you acquired the radio legally.
http://www.kenwoodusa.com/Contact/
Here's a forum thread I found from the results about this very topic:
http://forum.ecoustics.com/bbs/messages/4/146082.html
KCAR is a default code, it may work, it may not, it's worth a shot.
I often say it's not best to bash a newbie, because I found this site looking for a way to integrate my ipod better with my pioneer deck. I went through a lot of the posts and found the possibility of installing a computer in the car intriguing, and did more research. I'm now pretty close to getting everything in and working. So to user750, if you are interested in installing a computer and need help with integrating it with your kenwood deck, then this is one of the best places for information. If you just want the code, and to live on with your life, maybe calling kenwood, searching google, or asking a local car audio shop for this information may be better places to turn that will give you faster results.