Detect 64bit system from 32bit WIX installer

I hav开发者_StackOverflow中文版e a 32bit WIX installer that installs a .NET based windows service. I need to use one external .dll that comes in 32bit and 64bit versions. Is there any way a 32bit installer can detect it's running on a 64bit machine? I want to then conditionally install the 32 or 64 bit .dll.

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Extending Morten's answer, I did this in Wix 3.6

     <Component Directory="INSTALLLOCATION">
        <File Id="msvcp100.dll_x64" Source="$(var.x64)\msvcp100.dll" KeyPath="yes" />
        <Condition><![CDATA[VersionNT64]]></Condition>
     </Component>
     <Component  Directory="INSTALLLOCATION">
        <File Id="msvcp100.dll_x86" Source="$(var.x86)\msvcp100.dll" KeyPath="yes" />
        <Condition><![CDATA[Not VersionNT64]]></Condition>
     </Component>

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Try this:

<Component Id="Component1" Guid="*">
  <![CDATA[Not VersionNT64]]>
  <File Id="File1" Name="1.dll" Source="c:\dlls\1.dll"/>
</Component>
<Component Id="Component2" Guid="*">
  <![CDATA[VersionNT64]]>
  <File Id="File2" Name="2.dll" Source="c:\dlls\2.dll"/>
</Component>

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Create a property with ProcessorArchitecture and get the value of this from registry. Based on this property create a CONDITIONAL FEATURE.