When trying to search for windows updates (applies to Vista and 7), the CPU usage maxes out at 100% and just sits there, never finishing the search or finding anything.
Download the latest version of WSUS Offline at http://download.wsusoffline.net/
Extract all files to a new folder on the desktop.
Run the UpdateGenerator.exe until it's done
Run the UpdateInstaller.exe in the "client" folder and reboot. Run and reboot several times.
Many recent updates should have installed.
Try normal Windows Update through Windows again.