Whats a good way to build a serial number so you can link that to a customer?

I usually put the number of the program (in this case 04 being the fourth program i've built) "." then a series of numbers and letters of the program name and then a short version of the major and minor version numbers, such as:
04.[something]ST31
This way i can tell by the serial number what program they are using, what version, ect.


I'm doing this in the about box so that the program reads all the data in from the project and version info automatically.
Later on i was going to have a registration box at the start so that this number has to be writen into it.
Any ideas anyone?