Found this through Google
Click Start, and then type cmd in the Start Search box.
Right-click cmd in the Programs list, and then click Run as administrator. If you are prompted for an administrator password or confirmation, type your password or click Continue
At the command prompt, enter the following commands (you may copy and then paste them by right clicking with your mouse and selecting paste), and then press ENTER after each:
net stop wuauserv
net stop bits
net stop cryptsvc
ren %systemroot%\System32\Catroot2 Catroot2.old
net start cryptsvc
ren %systemroot%\SoftwareDistribution SoftwareDistribution.old
regsvr32 wuapi.dll
regsvr32 wuaueng.dll
regsvr32 wucltux.dll
regsvr32 wups2.dll
regsvr32 wups.dll
regsvr32 wuwebv.dll
net start bits
net start wuauserv
net start Eventlog
exit
Reboot and try update again.