They do that.
Basically i want my customers to pay for their software and then be able to download it straight away. Also it has to be secure so that they cannot just find the directory with all the files in and have access to all the programs. Im thinking encryption would help there.
Does anybody have any tips or guides?
Thanks in advance.

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic