This morning, I found a substantial group of Windows XP, Media, and Explorer
updates indicated as needing download in the tray. I duly ran these.
Immediately after rebooting, my machine (a Dell Dimension 5150) became
unstable. Upon booting into my desktop, an error message appeared indicating
that there was an error in the Windows Genuine Advantage Module. More
distressingly, I was from then on unable to run *any* programs.

I went into safe mode and rolled back the system 24 hours. I restarted and
my machine ran in a stable fashion. I then re-downloaded only the four
specific Windows XP patches, as I consider these to be the most crucial since
I don't use IE or Media. These are (KB936021), (KB938828), (KB921503), and
(KB938829). After downloading these and rebooting, the instability
immediately returned, with the same error message. FWIW, my Windows XP Pro is
indisputably genuine (it came from Dell with the machine, over a year ago), I
have not changed my machine configuration an iota. Something in one of these
four patches seems to be causing a serious issue.

This has caused me a good deal of stress (my first reaction was, sorry to
say, to yell at my daughter, who had gone onto my machine subsequent to patch
installation without letting me know). Is anyone able to tell me how these
patches may be safely added? Right now, I have instructed Windows Update not
to download them, but that leaves several vulnerabilities, which I dislike. I
have not tried to isolate which patch is at fault (as I don't like repeatedly
rolling back the system). Thanks in advance.

Edward