If your computer is so messy that it takes you ages to find any file on it, you probably need an application like Berokyo.
With Berokyo you can create a kind-of virtual cabinet to manage all your files, conveniently organized by categories. The funny thing about this program is that it really looks like a cabinet, with its shelves and all, which you can customize with different skins and colors to suite your taste.
It's worth mentioning that Berokyo doesn't store the actual files, but rather shortcuts to them – which means that if you delete files in Berokyo you won't lose them, and also that you should rely on Berokyo as a backup file container.
Using Berokyo is simple. When you start it for the first time, the program will start creating the first categories with items from the Control Panel, My Computer, My Documents and other system locations. You're then free to add many new cabinets and categories as you need, and organize their contents any way you like. The program also includes a convenient search tool that works not only with your hard drive, but also with Google, Yahoo!, YouTube, Flickr, Wikipedia, Amazon and more.
The idea behind Berokyo is good, but I don't find it that handy for daily use. The cabinet-like design is distracting and takes up too much space. Also, it'll take you a long time to configure the program properly in order to make it really useful.
Berokyo lets you organize the content on your hard drive in virtual cabinets, making it easier to manage.