Microsoft stopped updating XP a couple years ago, but I can't get rid of the wuauclt.ext file

Microsoft stopped updating XP a couple years ago, but I can't get rid of the associated wuauclt.exe updater file which comes on once a day and slows everything down for about 5 minutes...
 
I scanned wuauclt.exe with Webroot and Spybot -- both said the file was clean.
 
I tried erasing wuauclt.exe but it kept popping back up with warning messages from Microsoft...
 
I used Webroot to block wuauclt.exe the next time it came on -- seemed to work for a day...
 
But the next day I get a red Webroot warning message saying it has found a threat called wuauclt.exe in the Windows/System 32 folder.  Okay, so I tried to get rid of it (per Webroot's recomendation message), but after removing it, Webroot rescanned and it found wuauclt.exe again... 
 
Tried removing it a few times -- same thing. Webroot doesn't seem to be able to get rid of this monster. Webroot removes wuauclt.exe, re-scans and there it is again. 
 
Any suggestions would be much appreciated.