wifi hotspot

hi there all can anyone tell me where i can get a good guide on how to set up a wireless hotspot using open DD-WRT on my linksys router,and free radius and apachi on windows so i can run phpmyprepaid.where i can have a fully working hotspot were user have to provide a username and password when they open there browser and there password will be valid to the time set on my radius server wich is running on windows not linux.thanks