The location of WebDev.WebServer.exe is "C:\Programme\Gemeinsame Dateien\Microsoft Shared\DevServer\10.0\" on my system.
OS: XP SP3 (german)
VS: Visual Studio 2010 Pro (german)
The WebDevReplacer.exe tools seems to test for "%ProgramFiles%\Common Files\..." which isn't there for me...
The temporary solution: Copy from "...\Gemeinsame Dateien\..." to "...\Common Files\...", run tool, copy back.
The solution: use %CommonProgramFiles% for tests.