It is really down right rude to automatically expect him/her to have a illegal copy of trainz just because he lost the serial number or can't find it. I have gone through this many times myself where I couldn't find the number simply because there isn't a standard place that the company's put it. Some put it on the back of the jewel case,or inside the case above where the DVDs/CDs go,on the back on the manual,inside the manual on 1 of the covers,on a piece of paper that is slipped into the manual,or shockingly enough they forget to put it on! It's amazing how that works....