Merge pull request StefanScherer#256 from jeritiana/windows-7-sp1

Check before installing Windows 7 SP1

scripts/win-7-update-sp1.ps1

@@ -1,3 +1,10 @@
+# First check if Service Pack 1 is installed.
+$os = Get-WmiObject -class Win32_OperatingSystem
+if ($os.ServicePackMajorVersion -ge 1) {
+    Write-Host "Windows 7 Service Pack 1 is already installed."
+    Exit
+}
+
 New-Item -Path "C:\" -Name "Updates" -ItemType Directory
 
 # Service Pack 1 is an absolute requirement. Installing updates from Windows Update
@@ -14,4 +21,4 @@ Start-Process -FilePath "C:\Updates\Windows6.1-KB976932-X64.exe" -ArgumentList "
 Remove-Item -LiteralPath "C:\Updates" -Force -Recurse
 
 Write-Host "$(Get-Date -Format G): Finished installing Windows 7 Service Pack 1. The VM will now reboot and continue the installation process."
-Write-Host "$(Get-Date -Format G): This may take a couple of minutes."
+Write-Host "$(Get-Date -Format G): This may take a couple of minutes."