I couldn't get a 1 year old Ubuntu CD to install on the machine I built two weeks ago. I had to download a pre-release version of Dapper just to get an OS running.

With Windows, at least, you *do* get a CD, and the CD will contain drivers which will work. So your brand new disk controller or network card or USB controller or whatever will be usable even during installation.

That's impossible with Linux, as the kernel APIs and ABIs both keep changing, so there's no way to ever deliver a driver see more for older kernels. You need to make sure you upgrade your kernel to the latest revision, which often entails upgrading your entire OS, just to use some recent hardware.