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 value to the path of your favorite Diff tool
(e.g. "C:\Program Files\Beyond Compare 3\BCompare.exe")
- Restart Fiddler
That's it!