UXTheme Patcher 4.0
This little application makes it possible to use custom themes in windows. Works on Windows XP, 2000, 2003 and the likes. It wont work on Windows 95/98/ME.
After the its installed you will have to restart your system, afterwards you can use the custom themes/ visual styles.
If you are all new to this, you might want to visit these sites:
WinCustomize (ed. site has changed)
Lots of info on how to customize your system, a list of applications that will change the look of your desktop.
Customize.org
This place has a lot of ressources; themes, styles and the like for various applications. Good place to find something usefull and stylish.
Here are to screenshots. The first one shows my current desktop with firefox and miranda open, which both are customized af tad more that what the windows theme does.

The second screenshots shows how the theme can look on a simple program like Microsoft Office Word 2003. This might illustrate the theme a bit better.
