I am trying to use windbg to research a hang dump file created on an x64 machine for our x86 process. This is a 4.0 x86 application, so just to get an unmanaged stack, I had to
I believe you will have to use the 32-bit task manager, located in C:\Windows\SysWOW64\taskmgr.exe to get a 32-bit dump.
More info here: http://blogs.msdn.com/b/tess/archive/2010/09/29/capturing-memory-dumps-for-32-bit-processes-on-an-x64-machine.aspx