I have DCS Blackhawk   
I downloaded a few months ago but had a launcher problem. 
Since then I reinstalled Vista got around to reinstalling DCS Black hawk and when I go to run it, I am asked for a serial number. 
I dont know where to find the serial number.   
I have a confirmation of purchase email with a transaction number but that is differerent (well it doesnt work and is the wrong format).   
Ok.... 
I have gone to the DCS black hawk home page - and checked my details 
I have a Transaction ID noted that may work - it looks like a different number and in the right format. 
hopefully thats it :)   Thanks in advance