SI 5 does not run natively on a 64-bit OS.
The way to go about this is to install Virtual PC on your 64-bit machine, then install the 32-bit OS and System Integrator on that virtual. We have been using this configuration in our test environment and it works very well.
Virtual PC is free and can be downloaded here:
http://www.microsoft.com/downloads/d...displaylang=en