here's a download page for windows 7 sp1 and other updates http://www.microsoft.com/en-us/download/details.aspx?id...
also read: http://support.microsoft.com/kb/2505743
the download link has links to .iso image and other updates. read the kb article too. excerpt:
Step 3: Visit Windows Update and Install Windows Updates KB2454826, KB2534366, or KB2533552 if offered
Run Windows Update and if you are offered the option to install update KB2454826, KB2534366, or KB2533552, install them. If you install the service pack from the Microsoft Download Center and do not install these updates, you could encounter a Stop error in Windows in rare cases.
These updates will automatically be installed when you install the service pack by using Windows Update. However, these updates are not automatically installed when you install the service pack from the Microsoft Download Center.