Dell has just this week started selling PCs without Windows preinstalled. Go to their site and search for the "n-series".
That sounds like an improvement. Maybe because of the popularity of Linux?
But in reply to Tomcorn, except for Dell and their "n-series", if I buy a computer with Windows from a major company, I'm 100% stuck with Vista, whether I want it or not as the OEM install? So unless I buy from Dell, I'm looking at finding a local supplier to build me a computer and install a copy of XP bought from Ebay.