Copied from another thread in case it assists anyone...
I had this problem when setting up a new PC from a W7 SP1 CD. Update ran for 32 hours, and then crashed when I tried to install 220 updates. As an added bonus Update backed out all the updates which had been installed.
I turned off automatic updates and ran Update again. It ran for 26 hours and I selected the only first 50 updates to be installed. This ran ok.
I then ran Update again, but after six hours I turned off the PC and went to bed.
I tried re-installing the Update agent, and tried running Update again, but after an hour I cancelled it.
I tried re-installing the Update agent, and run the fix tool for Windows Update that made two fixes. I ran the Update, and cancelled it after two hours.
I re-installed the Update agent, ran the Update fix tool, and installed
https://support.microsoft.com/en-us/kb/3102810 which is mentioned in this thread. Ran Update again, and two minutes later it said there was 200 updates for my PC.
For the future I have a W7 Update folder with (1) the Update Agent, (2) the Update Fix-Tool, and (3) KB3102810.
Lee