TinyLaF is a free
Java Look and Feel which can look similar to Windows XP or Windows 98.
With the assistance of the control panel, one can define component's properties and behaviour.
From now on, YQ-themes (formerly known as XP-themes) will run on all platforms supporting Java 1.4.
The other good news: a lot of fixes and improvements (refer to the readme), also painting speed was remarkably increased.
TinyLaF is released under the LGPL, you can download both sources and binaries at
http://www.muntjak.de/hans/java/tinylaf/index.html