SkyNetRising :
For windows update to work on fresh windows7 sp1, you will need to install update KB3112343 manually
Stop and disable windows update first, and enable after you have installed KB3112343 and rebooted.
https://www.microsoft.com/en-us/search/result.aspx?q=kb3112343&form=MSHOME
Without this update windows update causes 1 core to get utilized at 100%, hogs about 1GB of ram and never does any updating.
This is absolutely true. On a fresh install of Windows 7 SP1, windows update runs forever without updating. Windows 8.1 fresh installs have the same problem. Microsoft has a fix, KB3112343 for Windows 7.
You must install the update mentioned to get Windows Update working. Trust me, I just spent a week on this, and discovered the fix independently. Then I searched this forum for the upgrade number and found that others have already posted. So I'm just echoing, you must do this update on a fresh install of Windows 7 SP1 or Windows 8.1.
Here is how I found it on Microsoft's site by searching for update fails:
http://answers.microsoft.com/en-us/insider/wiki/insider_wintp-insider_install/how-to-troubleshoot-common-setup-and-stop-errors/324d5a5f-d658-456c-bb82-b1201f735683
They say
"UPDATE: Microsoft recently released updates for Windows 7 and Windows 8.1 improving the stability of the upgrade experience for Windows 10. Please ensure you have the update installed for your respective version of Windows:
KB3112343 for Windows 7 and KB3112336 for Windows 8.1"
Microsoft needs to publicize this issue better to save us time and grief. Contrary to the above statement about merely improving stability of the upgrade process, this patch solves a serious problem. It corrects a total failure of Windows update. If you have this problem with either 7 or 8.1, you also can't upgrade to Windows 10 either, so you would think Microsoft would be more frank about this issue if they want people to move up to Windows 10.
So just do the appropriate update if Windows 7 SP1 or Windows 8.1 won't update. This is urgent. You need
KB3112343 for Windows 7 and KB3112336 for Windows 8.1.