Installing Windows 7 Service Pack 1
1. Visit the PC manufacturer's website and update
ALL drivers.
DO NOT use Windows Update or the "Update drivers" function of Device Manager.
2. Check Device Manager for any unknown/disabled devices - if there are unknown/disabled devices, fix them with the latest drivers from the device manufacturer's website (not the PC Manufacturer)
3. Visit Windows Update and get all updates
4. Visit Windows Update and get Service Pack 1 (usually under Important Updates). Read these notes for installing SP1:
Steps to follow before you install Windows 7 SP1 and Windows Server 2008 R2 SP1 from the Microsoft Download Center
5. Visit Windows Update and get any other available updates