To change your XP theme, you’ll first need to install either StyleXP ($19.95 ) or UXTheme Multi-Patcher (free). These programs enable Windows XP to use themes other than those made by Microsoft. Microsoft only has a handfull of themes available, so yeah, go ahead and install UXTheme Multi-Patcher; it's safe and can be uninstalled if need be.
UXTheme Multi-Patcher is a small download which simply allows you to install downloaded XP themes. This patch is for Windows XP and Windows Server 2003 only. Below is a link to custimize.org, which has a great tutorial on installing the patcher:
1) Install UXTheme Multi-Patcher
2) Download an XP theme to a folder of your choice. Unzip it if needed.
3) Select the .msstyles file. This will bring up the windows Display Properties dialog. From here you can click
I good site to check for cool XP themes: