To purify Shadow Lugia
Put Lugia in the purify chaimber set 1 and make it a best circle.Now make all other sets into best circles.(don't put any other shadow Pokemon into purification chaimber!!!!) Wait a while. Then you should hear a buzz and your controller should rumble indicating that it is ready. Go to Pokemon HQ lab and purify it.
P.S. I don't recommend purifing Lugia, but hey-it's your game!
P.S.S. I wouldn't go through the trouble. I don't think it's worth it.
More tricks, tips and cheats for this game are right here - Pokemon XD: Gale of Darkness cheats
Comments for this hint