My colleague can't - he bought a simple unit including Home Basic to keep the costs down, and DVDs are a foreign object to his PC. He was not happy to discover that when you buy Windows Vista, there are four versions and he was sold a pup.
On the other hand, another colleague who bought a Mac came into the office the other day with a DVD of his holiday fun at an off-road track. There's one version of Mac OS X, it contains everything, and you get iLife (iTunes, iPhoto, DVD, etc.) thrown in. He's a very happy bunny.
Terry speaks wise words, to be heeded...