Try:
Click Start
Type: cmd
Right click on cmd in start menu and select 'Run as Administrator'
Type: net stop wuauserv
Hit Enter
Type: ren c:\windows\SoftwareDistribution softwaredistribution.old
Hit Enter
Type: net start wuauserv
Hit Enter
Type: exit
Hit Enter
I tried this and it did not work for me since I don't see wuauserv running.
Attempt to download updates
It's probably because you've been/had been affected by trojan zeroaccess virus. Click on the windows icon and search for "run" . Right click on it, and run as admin. Now, type "services.msc" .IT will direct you to services. There, see if you have windows update
running. If you don't, then toy're missing a registry key. the "wuausersv" registry key.
To to the site given below :
http://www.smartestcomputing.us.com/files/download/9-registry-network-keys/ ( I found it while going crazy due to the same problem :P)
Download the file that resembles your version of Windows. Now, extract the bit. and wuauserv. file asnd double click on them. You'll be promplted if you want to allow registry rewriting. Keep going and after the process is done, restart windows. Now, again
go to run and type services.msc and you'll see windows update running. Problem : SOLVED