I would assume it's just about making sure the "confirm password" box does its job. Sometimes the clipboard isn't reliable (think screen sharing tools, this bites me all the time when a coworker and I are both looking at the same customer server). Sometimes you may think you hit ctrl-c but you really didn't for whatever reason, and now your password is whatever was sitting in your clipboard. Since they probably hide the password field you won't know what happened and your first interaction with their site will be the password reset page.

To be fair, the search is still on the start button if you just start typing. So you can hide the search box via the taskbar right-click menu and get that windows 7 feel happening. But of course the actual search results are another matter.

Sniglets!

Without prolonging the thread too much I just wanted to mention that I have an nVidia card which requires an additional plug from the PSU; however if you do not plug in the extra plug, the system will still boot into windows just fine. You then get a friendly reminder/warning when you log in from the nVidia driver that the card cannot achieve peak performance without the extra power. But it works just fine for non-game stuff. So I'm putting my money on Paul's theory.