lisence mangement

i was wondering wat a good license management program was i have seen .net seal cracked
and i was wondering wat a good one would be or if i should just get this one:
Oreans Technology : Software Security Defined.
thanks any advice is appreciated

Hmm? Registration keys?

Not too sure how you want to do it, but here's how I'd do it.

User buys program from website => server generates a key for him/her and stores it into a database (and echos the key to them.)
Program requires key to function (encrypt the local storage file where you are saving the key) => checks key to database
if key is already used or not valid, do not allow usage of program, else allow usage of program and set key to "used"