This one is just in time for Halloween here in the US on 31 October.  This new theme from the Windows 7 Personalization Gallery will bring some spooky backgrounds and sound effects to your Windows 7 computer.

Horse on Cobbled Street, Prague, Czech RepublicProfile of a CrowFull moon covered by a layer of clouds, 31 Oct 2009, Portugal
Fruit Bat Hanging from BranchMysterious Forest in the Pacific NorthwestPumpkins
Owl with Yellow EyesBare Trees at Night, Venice, ItalyMysterious Gate with Textured Wall, and Two Bats in Flight
Gargoyle on Building at NightCharles Bridge crossing the Vltava river in Prague, Czech RepublicFog in Copou Park, Iasi, Romania
Harvest Moon through Clouds, October 6, 2006, CanadaA Jack-o-Lantern in a Pumpkin Patch, CanadaBranches Surrounding Harvest Moon

Download the Eerie Autumn Windows 7 Theme