As for users databases, ACS 3.2 has been tested with Windows 2000 SAM database with Service Pack 3. As far as installing it on a Windows 2003 server these are the only requirements for ACS 3.2:
Hardware Requirements
For implementation of Cisco Secure ACS Windows, your Windows Server must meet the following minimum hardware requirements:
Pentium processor, 550 MHz or faster
256 MB RAM
250 MB free disk space, more if you are running your database on the same device
Minimum resolution of 800 x 600 with 256 colors
I'm sure the same is for ACS 3.1 as I am running it now on Windows 2000 server with AD authentication.
Helpful link: http://www.cisco.com/en/US/partner/products/sw/secursw/ps2086/index.html
Curt
