This week's book giveaway is in the OO, Patterns, UML and Refactoring forum. We're giving away four copies of Refactoring for Software Design Smells: Managing Technical Debt and have Girish Suryanarayana, Ganesh Samarthyam & Tushar Sharma on-line! See this thread for details.
I don't know anything specifically about IIS, but in general, it's the application itself that would have to support DELETE. Most web servers will implement all of HTTP. Does the application support it? Very few applications implement this -- for obvious reasons!