The Server.MapPath method can be used to retrieve several interesting properties about the running ASP application, for example:
' the current directory
currDir = Server.MapPath(".")
' the parent directory
parentDir = Server.MapPath("..")
' the application's root directory
rootDir = Server.MapPath("/")
For example, you can store the application's root directory in an Application variable, and use it to dynamically build physical paths to other files and directories.