Path to MSBuild

Poking around the registry, it looks like

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\MSBuild\ToolsVersions\2.0
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\MSBuild\ToolsVersions\3.5
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\MSBuild\ToolsVersions\4.0

may be what you're after; fire up regedit.exe and have a look.

Query via command line (per Nikolay Botev)

reg.exe query "HKLM\SOFTWARE\Microsoft\MSBuild\ToolsVersions\4.0" /v MSBuildToolsPath

Query via PowerShell (per MovGP0)

dir HKLM:\SOFTWARE\Microsoft\MSBuild\ToolsVersions\

You can also print the path of MSBuild.exe to the command line:

reg.exe query "HKLM\SOFTWARE\Microsoft\MSBuild\ToolsVersions\4.0" /v MSBuildToolsPath

If you want to use MSBuild for .Net 4 then you can use the following PowerShell command to get the executable's path. If you want version 2.0 or 3.5 then just change the $dotNetVersion variable.

To run the executable you'll need to prepend the $msbuild variable with &. That will execute the variable.

# valid versions are [2.0, 3.5, 4.0]
$dotNetVersion = "4.0"
$regKey = "HKLM:\software\Microsoft\MSBuild\ToolsVersions\$dotNetVersion"
$regProperty = "MSBuildToolsPath"

$msbuildExe = join-path -path (Get-ItemProperty $regKey).$regProperty -childpath "msbuild.exe"

&$msbuildExe