spld (and splfr) are command line tools and need to have access to a working C compiler and linker. This is typically not a problem on UNIX-like systems but on Windows there are some special steps needed in order to set up the environment so that the C compiler can be used.
The easiest way to get a command prompt where the C compiler works is to open the ‘Visual Studio 2005 Command Prompt’ from the Start menu. On Windows Vista this is located under ‘All Programs/Microsoft Visual Studio 2005/Visual Studio Tools/’. This opens up a command prompt where cl.exe (the C compiler) can be found via the PATH environment variable.
An alternative is to run the Visual Studio set up script from the command prompt, something like:
C:\>"C:\Program Files\Microsoft Visual Studio 8\VC\vcvarsall.bat" x86
This is in fact what the ‘Visual Studio 2005 Command Prompt’ shortcut does.
Once the environment is set up for using the C compiler you should be able to use the spld (and splfr) tools without problem.