For problems that can't be solved with Google, I usually turn to my Ultimate Windows Boot CD or a Knoppix boot CD. As long as the hard drive is not dead you can do just about anything with those.
I have about 120 workstations and a smaller site in China, but honestly I don't have to crack open any special software more than a few times a year. I have been playing with a network monitoring tool called PRTG lately though, and I like that. Nessus for security stuff.
McAfee, Ad-Aware, Spybot, Eusing Registry Cleaner, smitfraudfix, Process Explorer, Handy Backup, Kiwi syslog stuff, Hijackthis, sysinternals tools...Other than that, Google, Experts Exchange and Safari Books Online are about all I use.