I keep Windows 7 and Vista on my flash stick, written to there by Ultra ISO Bootable tab per this tutorial: USB Windows 7 Installation Key Drive - Create
When you first write either OS to the stick, it will place the seven files in the open root. When I am not installing either OS, I keep the files for each in their own separate folder. That way, I only have to spill the files of whichever OS I want to boot out into the root and it will boot per normal - either Vista or Windows 7.
I also keep all of my apps, utilities, tools and a copy of XP 9-in-1 on this stick and never go anywhere without it in my pocket.
One of the tools I use most is the Belarc Advisor which will audit all of your hardware, software, installed updates, license keys, etc and present a printable report.