1) Finding these keys in the memory space of WinDVD is an elementary reverse-engineering operation, hardly cutting-edge "cracking".
2) This is a software player; The key will be removed from the allowed list on all future hd-dvds, and the next point release of WinDVD will contain a new key + better obfuscation and anti-debugging code.
3) Before someone says how software will always be cracked blah blah, do note that:
3a) The media piracy "scene" (movies, etc) does not traditionally attract a large number of skilled reversers, for obvious reasons.
3b) Software can infact be made extremely hard to crack; I won't bother mentioning specifics since anyone who doesn't have an idea of what I mean probably wouldn't understand the explanation anyway