You may encounter the problem with Windows Update to take an extreme amount of time to search for updates. Additionally, the Windows Update process (part of svchost.exe) runs at 100% CPU time and uses a large amount of memory.
You can resolve this by installing the optional KB3102810.
If you are installing a fresh copy of Windows 7 / 2008R2, it is also highly recommended to install KB3112343 before searching for other updates. This considerably speeds up the search for updates.