How do I stop Windows Vista showing my last accessed files?

The solution is quite easy and is two clicks away in Microsoft Vista, actually. In fact, it's exactly the same as the solution to this question for Microsoft Windows XP too, now that I think about it. Here's what you do...

Right click on the Start menu icon (the fancy circle in Vista or the "START" button in WinXP). You'll see this:

As you can see highlighted, you'll want to select Properties. Now you'll get a window that has four tabs of material you can fine-tune, the most important tab of which is "Start Menu". On it you'll see:

That's where you can disable the most recent applications / most recent documents lists from your Start menu, as you can see in the picture above. By default it shows and displays this, but I also tend to disable it since I have a very good idea of what I'm working on anyway and don't typically need the shortcuts.

Note that many modern applications also keep their own list of recently edited documents too, including Microsoft Word, Adobe Photoshop, and the like. If you need to remove those lists too, you'll have to dig into the preferences of each app. Y'know, another solution that might be easier would be to set up a different user account in Vista. When you're going to walk away from the computer, instead just switch to "guest" and then it won't show anything you've done in applications or at the OS level...

Hope this helps you get the most out of Vista!