Starting tomorrow, Microsoft will begin rolling out Windows 7 Service Pack 1 (SP1) on Windows Update.
Windows 7 SP1 was previously available on Windows Update but required user action to install. Starting tomorrow, the installation will be fully automatic with no user action required for those who already have Automatic Update enabled. SP1 will be released gradually over the coming weeks on the RTM version of Windows 7. Microsoft warns that the service pack will take slightly longer to install compared to other updates. To ensure Service Pack 1 is installed without issue, you should check for sufficient free disk space and that AC power is present on a laptop. If additional space needs to be created, you may use the Disk Cleanup tool to delete some files so that the service pack will install. If the service pack installation is interrupted, it will reattempt to install automatically after the next restart.
This update only applies to Windows 7 consumer PCs that are not managed by a Microsoft management tool such as Systems Center Configuration Manager (SCCM) or WSUS Server. SCCM and WSUS administrators still have full control over the release of Service Pack 1. This remains unchanged.
As a note, Microsoft will no longer support Windows 7 RTM (with no service pack) as of April 9th, 2013.