Does changing build options move where an application is located in the Local Machine Software registry key?
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I have a solution where the executable's target platform was initially set to `x86`, many other projects were set to AnyCPU, and included 3 projects in .Net 3.5 (everything else .Net 4.0). I presume this is why the installer wrote to the `HKEY_LOCAL_MACHINE\SOFTWARE` registry key. 

Recently, I fixed some issues and now all projects are .Net 4.0. Additionally, I set the executable target platform to AnyCPU. I found the application was now installed in `HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node`.  

We develop currently with VS2010 on Windows 7 (64-bit) machines.
My question is: Did the installer write to `\SOFTWARE\` **initially** because some of the projects were .Net 3.5?

Also, if this application is intended to be installed on WindowsXP (32-bit is expected to be supported) machines, is the registry key problematic? Better yet, what should I look for in build options that ensures compatibility on WinXp 32-bit systems?