You need to be running the debug build of the dll's. Then you need to
attach a debugger. If you have VS installed on the same machine, then open
the solution and go to DEBUG\PROCESSES and attach the aspnet_wp.exe process
and set a breakpoint.
If it is running on another machine you can either install remote debugging
on the server, which is on the Visual Studio Disk 1 instller.
Or you can use a more lightweight debugger on the server, like cordbg.exe,
available with the .net framework. or WinDbg from