SharePoint 2010: Branding : changing UIversion of SharePoint Site

changing UIversion from 4 to 3 will give a look and feel like SharePoint 2007 site.

changing it back to 4 will make Visual upgrade to SharePoint 2010 site.

You can change UIVersion using PowerShell:

$web = Get-SPWeb http://server/site/
$web.UIVersion = 3
$web.UIVersionConfigurationEnabled = $true

You can also change UIVersion using feature receiver:

Hope that helps…