Of course, because malware can cause the issue, please download Malwarebytes from the link below, then install, update, and run a full system scan using the free program.
http://www.malwarebytes.org/
If that doesn't help, then please try the steps below:
Re-register the Windows Update DLL with the commands below
Click Start, then type: then type cmd in the search box, and when it's displayed at the top of the search box, RIGHT click on cmd.exe, choose "Run as administrator" from the little menu.
When the command windows loads, type the following commands at the blinking cursor. Press ENTER after each command.
regsvr32 wuapi.dll
regsvr32 wuaueng.dll
regsvr32 wuaueng1.dll
regsvr32 wucltui.dll
regsvr32 wups.dll
regsvr32 wups2.dll
regsvr32 wuweb.dll
Close the command window and reboot the computer. Attempt to run Windows Update
Hope this helps.
Grif
For the past 2 days I keep getting an error message Code 80004002 which says Windows update encountered an unknown error. Updates cannot be accessed at all. Microsofts FixIt when used says the problem is corrected but it is not. Their other alternatives page has been discontinued. Vista 64 bit is supposed to be supported until Early 2014. What can I do?

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