15 Admin Tools
...you can't do without (according to techtarget.com). More...

Shellview
A utility designed to help a user or administrator get a handle on shell extensions. More...

Audit Registry Changes
Say after an application install using a free command-line tool called Keytimes.exe. More...

Backup DNS
MCPmag has an article on how to backup DNS easily. More...

For example, here's how the contoso.com AD-integrated zone is backed up:
dnscmd /zoneexport contoso.com backup\contoso.com.dns.bak

Reskit.net
"This site provides good stuff for MCTs and other trainers". Lots of other interesting stuff too. More...

IPA.EXE and IPN.EXE
Two command-line tools that make name-to-IP and IP-to-name conversion easier.
More...

Defrag the Virtual Memory in Windows XP

The old way: delete the paging file, defrag the PC and recreate the paging file.

The new way: PAGEDEFRAG. When run, it will force a defrag on your page file the next time your machine is rebooted. You can also use it to force a defrag of the page file on each reboot! More...