Are you looking at the latest (version 7) or the previous (version 6) installation?
Both will support Windows 2003 Standard\Enterprise (32 bit ONLY).
Version 7 will support SQL Server 2005 (Standard, Enterprise, Express) ONLY 32 bit if on box, 64bit SQL if off box.
Version 6 will support SQL Server 2000 and 2005 (same restrictions as above).
IE 6 and 7 will work with v6, while v7 requires IE7
The systems cannot be installed on a domain controller.
(edit note: had toe clarify on the IE versions. NS7 requires IE7).