Ultimate Windows Tweaker
Remember Tweak UI for Windows XP? Microsoft never got around to doing a Vista version of the popular (but unsupported) utility, which lets users modify various aspects of XP's interface and operation. Fortunately, there's a third-party alternative: Ultimate Windows Tweaker, which the developers bill as "Tweak UI for Windows 7 and Vista."
Designed for advanced users (but worth a peek for ambitious novices), UWT gives you control over more than 130 Vista settings, all of them conveniently grouped into seven categories (Personalization, Security, Internet Explorer, and so on). Thankfully, you can get a description of any given setting just by mousing over it.
You can also create a system-restore point just by clicking a button in the UWT window--handy just in case a tweak goes awry. Or click Restore Defaults to set everything back the way it was.
My favorite tweak (so far) is Restore folder Windows at startup in the Personalization section. If I shut down or reboot with folders still open, those folders will re-open when Windows restarts. But there are countless others, like the option to restore the Run command to the Start menu. UWT is definitely a must-have for system modders, or anyone who likes to dive deep into Windows' guts (without mucking around in the Registry). It's free.