I remember having a problem with installing SP1 for W7, I had a look at my notes and found:
+++Install Windows Update KB2454826 from Windows Update (click here if it is not already installed. If you install the service pack from the Microsoft Download Center and do not install Windows Update KB245862, you could encounter a Stop error in Windows in rare cases.
Windows Update KB2454826 will automatically be installed when you install the service pack by using Windows Update. However, Windows Update KB2454826 is not automatically installed when you install the service pack from the Microsoft Download Center.
To check whether Windows Update KB2454826 is installed, click Start, type View installed updates in the Search programs and files box, and then press Enter. Notice whether Update for Microsoft Windows (KB2454826) is listed. If the update is not listed, you will have to install it from Windows Update (click here .+++
since then I've downloaded an .iso file of W7 with SP1 Update (media refresh) already on it and burnt it to DVD so when I reinstall or do a sfc /scannow I don't have problems.
I downloaded from official Microsoft link given on Heidoc.net (scroll down to the English USA versions)
This thread is now locked and can not be replied to.