I use the awesome Fiddler2 to debug HTTP, and I needed to compare sessions. Fiddler has a support for this, but when I clicked Tools - Compare Sessions, it prompted me to install Windiff.exe. I haven't found a way to set the preferred Diff tool in the UI (via Options), so after looking at the click handler for the menu in Reflector, I found out that the value can be set via Registry key: Open Registry, go to: HKEY_CURRENT_USER\Software\Microsoft\Fiddler2 Add a new String Value called CompareTool and set the...