They might have to make a "lighter" version of Vista, because the cheap Dell's are only 2.6 Ghz Celerons, with 512MB of memory and integrated graphics, and Vista will be unresponsive on those machines.
Really stupid time to release an OS as most of the hardware venders bring out there new stuff come chinese new year.
Meanwhile the rest of the computer industry is still half asleep as they are on holidays or recovering from christmas / nye hang overs.
Unless Microsoft offers a bonus upgrade with Windows Xp PCs, this will affect computer and notebook sales in the final quarter of 2006 as most (dumb) end users want the latest OS.