From a service that is not running to malware damage. Let's start with Services.
Read http://www.blackviper.com/wiki/Windows_Update
Sorry but it is fairly technical but you can now check if those services are running.
Bob
Hello, I would like to do Windows updates on Vista. However, When I click to do the updates I get this pop up with a message stating
"Windows Update cannot currently check for updates, because the service is not running. you may need to restart your computer"....
I restarted several times but it 's not working. Can anyone help please? Thanks

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic