Make up your mind: your question seems to imply two incompatible application types.
Your title talks of a "Desktop application", then the body starts talking about pages, and the subject is ASP.NET which is web based. You cvan't create a desktop application that runs from a web site - security will not allow that.
If this is a web site, then look at implementing Membership: Introduction to Membership
] which makes the process quick, easy and reliable.
If this is Windows Application based, then that is not a question we can just give you an answer to - there are far too many variables. For example, what do you want to use for storage? MsSql? MySql, SqlLite? SqlCE? XML? Excell? Access? Oracle? Text files? I have seen them all used with varying degrees of success. You need to sit down, think about what you want to do, and what tools you have at your disposal. Then ask again, giving as much detail as appropriate, or you may find that the process of thinking about it solves the problem anyway...