From Microsoft Technet:
Whether you install 32-bit or 64-bit, Virtual PC 2007 or Windows 7 Virtual PC, you will only be able to install 32-bit virtual machines. Install 64-bit Virtual PC 2007 or 64-bit Windows 7 Virtual PC on a 64-bit version of Windows 7.
Whatever virtual machine you create will work perfectly on a 32-bit machine. A Virtual PC virtual machine made on a 64-bit version of Windows is exact;y equivalent to one made on a 32-bit version of Windows. There is absolutely no reason whatsoever to install 32-bit Virtual PC (any version) on 64-bit Windows.