Since most legitimate vendors are no longer able to sell or install Windows XP after June 30, I have an option for you: Use Linux. That's right, retain that XP look and feel goodness without violating any rules or creating other problems for yourself by using the little known XPDE (XP Desktop Environment). Even better, you install it on the uber-goodness (and freeness--is that a word?) of Linux.
The good folks at XPDE offer you an almost exact replica of the XP Desktop on Linux.
Familiar XP icons, taskbar, and cascading menus coupled with the speed and stability of Linux is just what you need to continue the XP legacy.
I know I'm the Linux maven in these here parts but I appreciate good software no matter where it comes from and XP is good. It's so good in fact, that I support the effort to keep it alive. XP is so good that the large (100K+ employees worldwide) company I work for isn't switching to Vista. IBM isn't switching either.
Projects like XPDE and Wine make it that much easier for companies, individuals, and governments to make the switch to Linux. Armed with the XP Desktop Environment, Microsoft Office and other applications under Wine, and Linux under the hood: It just doesn't get any better than that.