A REALLY nerdy tool and a live boot.
nLite
Windows XP slipstreamer.
For those less tech savvy, it lets you build a custom XP install disk. Everything from adding the correct SP or patch to customizing the GUI, adding users, auto-login, and adding DRVIERS. You can also have it auto-install and auto-include your CD key. While it's probably aimed partly at businesses, it's awesome if you need to install XP relatively often (guilty) or you happen to have an army of window XP VMs (also guilty).
And if you don't know about this one you should probably be shot...
Knoppix Linux
The original Live-Boot disk. Runs like a charm and is great for backing up data when windows decides it wants to randomly stop booting correctly. It works with EVERYTHING... just lovely.