Of course, it helps to know which item was being "updated", AND to know you have ruled out any conflicts with startup programs & all other programs that were running ! You must minimize (ideally) running progs to a barebones minimum.
1) Use Windows task Manager ( CTRL+ALT+DEL keys) , look for a program that's running--similar to "update.exe". Then "end" that task.
2) do cleanups: Follow these steps & this article for cleanups and Insure you do not have a leftover "Catroot2" sub-folder !
Bring up Windows Explorer / Tools / Folder Options/ select VIEW Tab and look at all of settings listed.
"CHECK" (turn on) Display the contents of system folders.
Under column, Hidden files and folders----choose ( *select* ) Show hidden files and folders.
Next, un-check Hide extensions for known file types.
Next un-check Hide protected operating system files.
Use Windows Explorer. Go to C:\Windows\System32
If you have a sub-folder called * Catroot2 * (not Catroot) rename the
folder to CR2OLD. Or delete everything in that folder. Just make sure you do the right one.
This is for all editions of Windows. Just follow section for your version:
Read, study, and do what this article recommends. One of the things you will do
is to *very carefully* remove some files from the WUTEMP folder ; plus some more.
WINUP: Error Message: "Software Update Incomplete, This Windows Update Software Did Not Update Successfully
3) Try looking at your log file & try to see if there is an "error" for the date(s) when you had this problem.
It will have an entry (entries) with Error that would help to pin-down your pc's problem with Windows Update on-line functions.
C:\Windows\Windows Update.log (for Win XP & Win98/Me)
See MS Windows Update Troubleshooter
MVP Windows - Shell / User