The Windows 8 Preview is able to use AMD Bulldozer's multi-threaded execution scheduler engine, but Windows 7 has not. Microsoft now has a hot fix to enable this in Windows 7 as well. PC Per estimates you could see up to 10% performance improvement in some multi-threaded applications.
http://www.pcper.com/news/Processors/Microsoft-Releases-Update-Improve-Bulldozer-Performance


