Are you getting bored with windows xp themes and tools and cannot afford to upgrade to Vista.
There are some tools which help in transforming your xp themes to vista themes. Most popular is Vista Transformation Pack 7.0.exe by Windows X. I personally tried and is a very good tool.
There are few other tools for windows XP provided by Microsoft – Microsoft Power toys
some of them are Power Caculator, Image resizer, Virtual Desktop manager ( like we have in Linux) etc.