chef-windows-guards.rb

##### Check if an application is installed.
# In a lot of cases an MSI doesn't properly get detected by the Chef windows_package resource or is some pther package type. The best approach is to use a guard which checks the uninstaller regkey to check that the package and version exist as a Guard. Note: Replace the items inside the "<< >>" notation with the appropriate name and version. I'll usually use an attribute to allow for changes to be applied at an environment or role level.

#### X64 bit detection or native 32 bit
not_if <<-EOH
  $installed=Get-ItemProperty HKLM:\\SOFTWARE\\Microsoft\\Windows\\CurrentVersion\\Uninstall*|where {$_.DisplayName -eq \"<<SOFTWARE DISPLAY NAME>>\"}
  if ($installed) {
    if([system.version]$installed.DisplayVersion -ge [system.version]\"<<SOFTWARE VERSION NUMBER>>\"){$true}else{$false}
  }
  else
  {$false}
EOH

##### X86 bit detection on a X64 bit architecture
not_if <<-EOH
  $installed=Get-ItemProperty HKLM:\\SOFTWARE\\WOW6432Node\\Microsoft\\Windows\\CurrentVersion\\Uninstall*|where {$_.DisplayName -eq \"<<SOFTWARE DISPLAY NAME>>\"}
  if ($installed) {
    if([system.version]$installed.DisplayVersion -ge [system.version]\"<<SOFTWARE VERSION NUMBER>>\"){$true}else{$false}
  }
  else
  {$false}
EOH

#Check if an ISO is mounted.
not_if "((gwmi -Class Win32_LogicalDisk | Where-Object {$_.VolumeName -eq \"<<VOLUME NAME>>\"}).VolumeName -eq \"<<VOLUME NAME>>\")"

Note Guards that use powershell code need the guard_interpreter set to :powershell_script otherwise they will silently fail.