Microsoft offers Visual C++ 2005 Express Edition for free. As it ships, it's almost ready to build BFilter, except it's missing the Platform SDK, which is fortunately available for free as well.

1. Download and install Microsoft Windows Platform SDK. Don't worry, you won't have to download all those 400 megs. The thing is named "Windows Server 2003 SP1 Platform SDK", but it works fine on Windows 2000 and above. Download PSDK-x86.exe, launch it and select custom install. Just one component is necessary:
   • Microsoft Windows Core SDK -> Build Environment -> Build Environment (x86 32-bit)
2. Now you may follow instructions that Microsoft gives for integrating PSDK into Visual C++ 2005 Express Edition. This step is not really necessary, as we are not going to use the IDE, just the command-line tools.
3. Now you need to edit $VSDIR\Common7\Tools\vcvars32.bat, where $VSDIR is the path to Visual Studio installation, which is usually C:\Program Files\Microsoft Visual Studio 8.
   Open vcvars32.bat in Notepad and put the following to the bottom of it:
   

   Set PSDK=C:\Program Files\Microsoft Platform SDK Set PATH=%PATH%;%PSDK%/bin Set INCLUDE=%INCLUDE%;%PSDK%/include Set LIB=%LIB%;%PSDK%/lib