Starting today Microsoft will begin rolling out Windows 7 SP1 automatically through the pre-installed Windows Update to Windows 7 users who still are running the RTM (release to manufacturing) version without SP1 installed.

Microsoft posted more details on it’s Blog.

Starting tomorrow, Windows 7 Service Pack 1 (SP1) will begin rolling out automatically on Windows Update.  Updating customers to Windows 7 SP1 is part of our ongoing effort to ensure continued support and improved security updates for customers who have not yet installed SP1. 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 to all customers on the RTM version of Windows 7.  The service pack will take slightly longer to install compared to other updates.  To ensure Service Pack 1 is installed without issue, customers should check for sufficient free disk space and that AC power is present on a laptop.  If additional space needs to be created, we recommend using 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 mentioned by Stephen Rose here on the Springboard Series Blog – Windows 7 RTM (with no service pack) will no longer be supported as of April 9th, 2013.

If you have any issues with the installation of Windows 7 SP1 through Windows Update, please visit this support page on Windows.com or our Microsoft Community forum for Windows 7.