Microsoft today has released a performance and a reliability update for Windows Vista. This is one of the steps towards Windows Vista Service Pack 1.
Update for Windows Vista (KB938979)
This is a performance update. Install this update to improve the performance of Windows Vista in certain scenarios.
Update for Windows Vista (KB938194)
This is a reliability update. Install this update to improve the reliability of Windows Vista in certain scenarios.
I highly recommend installing both these updates.