Windows SP1 may not appear in Windows Update if certain versions of SafeCentral are installed on your computer. SafeCentral is a security program that is manufactured by SafeCentral, Inc.

If your computer is running SafeCentral version or an earlier version, you have to update SafeCentral before you can install Windows 7SP1.

Windows 7 SP1 will not appear in Windows Update if update 2454826 is not installed. Windows Update will not offer you update KB2454826 if you are using one of the following Intel integrated graphics drivers:

- Igdkmd32.sys (32-bit), versions through
- Igdkmd64.sys (64-bit), versions through

Make sure that you did not use vLite to customize your Windows 7 installation. vLite is a third-party program that is used to customize an installation of Windows 7. vLite is known to remove some Windows system components.

Full read at KB2498452.