Term not recognized as name of a cmdlet, etc.

In Visual Studio Ultimate 2012, I specify a post-build event that should execute a powershell script. In the Post-build event command line, I specified:

"C:\Windows\system32\WindowsPowerShell\v1.0\powershell.exe" -ExecutionPolicy Unrestricted -NoProfile -NonInteractive -NoLogo -file "$(SolutionDir)..\docs\create_api_documentation_post_build.ps1"

Now, when I build the project and look at the VS Output window, I find this:

------ Build started: Project: InformationHub, Configuration: Debug Any CPU ------
  InformationHub -> C:\...snip...\InformationHub\bin\InformationHub.dll
  C:\Windows\System32\msxsl.exe : The term 'C:\Windows\System32\msxsl.exe' is not recognized as the name of a cmdlet, function, script file, or operable
  program. Check the spelling of the name, or if a path was included, verify that the path is correct and try again.
  At C:\Users\eric\Documents\GitHub\CIH\MvcWebServices\docs\create_api_documentation_post_build.ps1:3 char:1+ C:\Windows\System32\msxsl.exe -o "$scriptPath\InformationHub.html" "$scriptPath\ ...+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~+ CategoryInfo          : ObjectNotFound: (C:\Windows\System32\msxsl.exe:String) [], CommandNotFoundException+ FullyQualifiedErrorId : CommandNotFoundException

  C:\Windows\System32\msxsl.exe : The term 'C:\Windows\System32\msxsl.exe' is not recognized as the name of a cmdlet, function, script file, or operable
  program. Check the spelling of the name, or if a path was included, verify that the path is correct and try again.
  At C:\Users\eric\Documents\GitHub\CIH\MvcWebServices\docs\create_api_documentation_post_build.ps1:4 char:1
  + C:\Windows\System32\msxsl.exe -o "$scriptPath\MrdDataServices.html" "$scriptPath ...+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~+ CategoryInfo          : ObjectNotFound: (C:\Windows\System32\msxsl.exe:String) [], CommandNotFoundException+ FullyQualifiedErrorId : CommandNotFoundException

------ Build started: Project: TestDataServices, Configuration: Debug Any CPU ------
  TestDataServices -> C:\...snip...\TestDataServices\bin\Debug\TestDataServices.dll
========== Build: 2 succeeded, 0 failed, 1 up-to-date, 0 skipped ==========

So, it seems it can't find msxsl.exe.

However, when I run that same command (with the $(SolutionDir) keyword expanded) on the commandline (cmd.exe), the powershell script is executed without problem. 

Can somebody explain what is going on here and how to make it so that my post-build powershell script will be executed post build?

Thanks

Eric