I tried & tried & tried & was giong nutso, couldn't get rid of this thing.
Finally, from safe mode, I loaded up an old DOS utility from my 286 days, this was written in 1993. That utility actually let me see the file, then I could change the attributes so I could see it at the command line. Probably an ol Norton Commander would do the same thing.
I rebooted to safe mode command line, went back to windows\system32 & manually deleted the file.
I then ran the regedit, got rid of the entries that loaded the ugly beast,
rebooted XP in all its glory, checked the running pocesses, & no more wuamgrd.exe, gone, done, finished.
Ye haaa!