Installing AlienGUIse Theme Manager to Windows XP x64 Platform

I'm trying to install AlienGUIse Theme Mnanager to Windows XP x64 platform, but failed to install.

http://support.alienware.com/Support_Pages/Restricted_Pages/driver_downloads_processed.aspx?os=WXP64&cat=&manu=&item=

[AlienGUIse™] Xenomorph

After I downloaded above driver and started the installer, following error message displays.

This Theme Manager installer does not support Windows x64 platforms.

My understanding is this driver does support Windows XP x64 platform, why can't I install it to my PC?

I need your kind help!