If your computer is set to automatically install updates, you'll be prompted by Windows Update to install SP1. Follow the instructions on the screen. If you aren't prompted to install SP1, follow these steps:
Make sure your computer is connected to the Internet.
Click the Start button The Start button, click All Programs, and then click Windows Update.
In the left pane, click Check for updates.
If any important updates are found, click the link to view available updates. In the list of updates, select Service Pack for Microsoft Windows (KB976932), and then click OK.
Click Install updates. Administrator permission required If you're prompted for an administrator password or confirmation, type the password or provide confirmation.
Follow the instructions on your screen.
After the installation is complete, log on to your computer at the Windows logon prompt. You might see a notification indicating whether the update was successful.
If you disabled your antivirus software, enable it again.