I am looking for a way to uniquely each PC that uses my application. My application uses a database so I can write a record with the licence number and the unique key I am looking for. If I see the same licence number with two different unique key then I will know something is wrong. I know there are ways like CPU number, HD number, etc... I need something that will run with any cpu that runs Windows. I can assume all PCs will have a hard drive.