Portable OpenVPN - VPN Server

I need a VPN server based on OpenVPN. - A downloadable *.exe file based on portable OpenVPN [login to view URL] - When installing this file on XP, Vista, (optional Windows 7)the keys will be generated automatic and match how ever with the key on the VPN server. - The VPN on the client PC is running for a special period, e.g 2 days. - User can buy a 1 year licence, after 1 year it has to stop working, but he can continue by buying another year. You have to make a database. - Somewhere a link to a buy it now page The installation for the clients should be easy and simple. Payment after the job is done. Any questions let me know.