Wal-mart offers several low-cost notebooks with Microsoft Windows Vista pre-installed.

The Everex StepNote VA4101M notebook with 15.4 inch screen, 1.46GHz Intel Celeron M Processor 410, 512MB, 60GB HDD and DVD drive sells for $498. You only get Windows Vista Home Basic with this deal on Wal-mart. If you just need a notebook to surf the web and other basic tasks then Basic is fine. You will not get Aero with Basic. The specs of this notebook would not allow it anyway as far as I can tell.
Microsoft has this helpful and concise comparison table comparing the different Windows Vista editions.

See the full list of low-cost Vista notebooks on Wal-mart.