John Robbins over at Wintellect: http://www.wintellect.com/CS/blogs/jrobbins/default.aspx
Tess Ferrandez an ASP.NET Escalation Engineer at Microsoft: http://blogs.msdn.com/b/tess/
Loading SOS In The Immediate Window
With that said, let's take a look at what it takes to get SOS going in the Immediate Window. As we go along I will also show you the most common messages you will encounter when trying to set this up. First, open the Immediate Window (CTRL + ALT + I) and put in ".load sos" then press ENTER.
x86
You will most likely get this message:
"SOS not available while Managed only debugging. To load SOS, enable unmanaged debugging in your project properties."
The fix is, obviously, to go to your project properties (the Debug tab):

Read more: Visual Studio Tips and Tricks