If you still cannot Update Windows Vista using WindowsUpdate, try this :

http://*.windowsupdate.microsoft.com
http://*.windowsupdate.com
http://update.microsoft.com
http://update.microsoft.com/microsoftupdate/v6/default.aspx

Else, note your error code and visit this excellent Microsoft Resource : Windows Update Support: Error Codes. Search for the solution against your error Code. If you receive Windows Update error 80246008 while downloading updates, you might need to change the Background Intelligent Transfer Service (BITS) or Windows Event Log service settings, and then restart each service. Click here for more on it.

KB943144 - Updates are not installed successfully from Windows Update, from Microsoft Update, or by using Automatic Updates after you repair a Windows XP installation

KB910337 : You may receive an error message that contains the "0x8DDD0018" code or the "0x80246008" code when you try to download updates from the Microsoft Windows Update Web site or from the Microsoft Update Web site

KB836941 : You may receive an "Error 0x80072EE2," "Error 0x80072EE7," "Error 0x80072EFD," "Error 0x80072F76," or "Error 0x80072F78" error message when you try to use the Windows Update Web site or the Microsoft Update Web site

KB883825 : You receive error 0x80070020 with error message, The process cannot access the file because it is being used by another process, when you use the Windows Update Web site or the Microsoft Update Web site to install updates.

If you are recovering from a malware attack, you may also want to have a look at your Hosts file. Some malware programs may modify the hosts file to control DNS name resolution. Remove ALL entries for Windows Update and Microsoft Update from your Hosts file situated at C\Windows\system32\drivers\etc\hosts