Quake3World

I have the Windows XP Professional Upgrade edition retail version, installed on one home computer (a system where I have over the years changed major components, like motherboard and hard drive, and re-installed multiple times).

If I were to create a dual-boot system with Vista/XP on my laptop, would XP complain about the installation on multiple systems? If so, any way around this so I can still get all the latest XP security updates?

The license you purchased for XP is only valid for one PC. If you want to use it on an another PC then you'll need to purchase another license.