Question: **Scenario:** In an e-commerce system, a helpdesk user should be able to "impersonate" or "log on as" a specific customer (from the web-based administration site) so that he can support the customer first-hand - eg. when the Customer is on the phone.

Additional clarification: There is no need to keep track of the original authentication context. We simply need to provide a "Log on as" button that will log on as the customer without the helpdesk user needing to know the password.

Any ideas how this scenario could be implemented using regular ASP.NET Forms Authentication?

Answer: 
Save the information about file to MySQL, and save the last time the image was viewed - can be done via some script that would be altered everytime the image is being used.. and check the database for images not used for 30 days, delete them..
Check the last accessed/modified time of file to see it if has been used.