As a Windows administrator, what tools do you feel you cannot live without?
Active Directory - if you manage a domain this is your best friend. It centralizes all control over users/computers/printers/groups in your organizational unit into one program.
gpedit - the group policy editor, allows you to easily manage registry entries for groups of users at a higher level.
regedit - Great for making lower level tweaks to the system not available through the group policies.
I still find myself firing up Sequoia View to spot the massive temp files/caches that can otherwise lie unnoticed on a volume.
Bart PE, with a large assortment of plug-ins. Not so much for day-to-day use but for all those times when things go wrong and normal tools won't help or when something can't be achieved while the regular OS is running.
Perl. Tools such as logparser might be OK for some jobs but Perl has no limits.
Robocopy. In my opinion the best readily available copy utility for Windows. If you have a copy/move/sync operation that you can't do with Robocopy it's time to read the manual again.
Joeware tools and Sysinternals
Remote Desktop Manager is awesome, It centralize all my remote connections (Including RDP, Putty, SQL Server, HTTP Interfaces, (S)FTP, CIFS shares, OpenVPN connections...
It's really a must have, all this for free, but the enterprise edition allows you some nice thing like storing connections settings in a database to push modifications to the others admins)
Heh... Norton Comander.. I like console (since DOS/Windows 3.x) and i use FAR Manager (farmanager.com) as my file manager for a long time.
Now new version (2.0) with Unicode support(!) is availible. And this version not shareware, it's FREE (BSD-like license). It's still in "alpha" and a bit tricky to install but fully working (even x64).
Richcopy, a released tool that used to be used internally in Microsoft. It's a ultimate copying tool that is much better than robocopy.