Sorry about your problem, arn't computers a pain sometimes.
Anyway, here I believe is your answer, it does work.
Assuming your os is win xp and located on your c: drive,
start- all programs - accessories - notepad
Cut and paste this into notepad:
Now click on File
Click on Save As
(dialogue box appears)
At the bottom do the drop down in Save as Type as ALL FILES
In File Name box name it Winupdatefix.bat
Save it to your desktop (for ease of finding it)
it will appear as a ms-dos batch file.
press enter after each confirmation. if it says it is missing a file or
cannot re-register don't worry. Note: initpki.dll will seem to hang, it
just takes less than a minute compared to the others (that are almost
Restart computer (optional)
Try to update again, it will work.