It really depends on how much power you want. For an enterprise-level tool, check out the Enterprise Configuration Manager from Configuresoft. From a web-console, you can modify registry values, change user passwords, run remote commands, gather thousands of pieces of data (file-structure, registry keys, device drivers, user/group info, etc), keep systems up-to-date with MS patches, create graphical reports based on user-defined values, and maintain compliance with government and industry requirements (such as SOX, HIPAA, DSS, etc).

Oh, and as a perk, it can do much of the same things for UNIX systems.