I am using IIS7 Express while developing my web application. I need to use fiddler to investigate an issue and cannot figure out how to configure things so I can get the HT
You can use fiddler as a proxy between your clients and the server. This means you start up fiddler, and then access the server using fiddler's port rather then the usual port (default for fiddler2 is 8888 I think). If you need to debug the server "live" vs. real world clients, you can change the IIS binding from :80 to something else, and place fiddler's proxy on port 80.
EDIT: By the way, by default fiddler2 changes the proxy settings on your browsers so that they access everything through fiddler anyway (on the machine in which fiddler is installed only)