i tried doing that at one point of time
But i was just bymyself, so i offered to sell the code rather than get thru this mess.
There are some 3rd party tools that help you do that!
(But they charge for it)
It depends on how you want to implement it.
You could put some info into a file, but everytime the program is unisntalled, the file is reinstalled and you have can give another 30 days per install.
not a good idea....so does storing this info in a database mean the same.
you could hoever embedd some info into the registry, and let it remain there even during uninstall.
Depends on how you want to implement it.
I would really like to follow this thread though!
Check
this library out, It also has an implementation of something that you can use