I like changing the appearance of my Windows XP often because the default styles look so boring and dull. For all those people out there who like changing their XP themes often you can try the StyleXP theme changing software if you want to blow off your PC memory or else you can read below for a simple tweak that will let you change your themes without eating any PC resources.
Using 3rd Party Msstyle Themes in Windows XP
UxTheme Multi Patcher is a very nice little utility that will patch your Windows XP so that you will be able to use 3rd Party Msstyle themes without requiring any additional software. This utility does a simple little trick by patching the uxtheme.dll file which is responsible for changing your Windows styles.
Download UxTheme Patcher and Windows Styles
Just don't forget to apply the patch before downloading and installing any themes.