Can you tell us, what software is that?
Anyways, running a virtual machine with a 32 bit OS installed might be a solution.
But switching a 64 bit into 32, I don't think there's such a thing, apart from reinstall. For what it's worth, check out this:http://windows.microsoft.com/en-us/windows7/32-bit-and-64-bit-Windows-frequently-asked-questions
If you want to move from a 32-bit version of Windows to a 64-bit version of Windows 7 or vice versa, you'll need to back up your files and choose the Custom option during Windows 7 installation. Then, you'll need to restore your files and reinstall your programs.