To use Server Side Includes:
The page that is calling the include must be one of the following file types
.asp .stm .shtm or shtml
The include being called must be .asp or .txt and have no head or body tags.
The virtual link must come down from the wwwroot directory
Eg:
Your include file is wwwroot/includes/top.asp
The virtual dir should be include virtual="/includes/top.asp"
This has been tested with Parent Paths On