At regular intervals, Microsoft issues Critical Updates for Windows. Everyone who knows me knows that I recommend configuring your system so that these updates get downloaded automatically. (But don’t choose the option to install them automatically; in that configuration, Windows will automatically restart itself in the middle of the night, even if you have unsaved files open!)
Every so often, one of these Critical Updates turns out to cause additional headaches. That’s the case with Critical Update 811493, which fixes a nasty security bug that could allow someone to take over a computer running Windows XP. Unfortunately, this fix doesn’t play well with some antivirus programs on computers that also have Windows XP Service Pack 1 installed, as Microsoft acknowledged in a brand-new Knowledge Base article: 819634 – You May Experience Performance Issues After You Install the 811493 (MS03-013) Package on Your Windows XP SP1-Based Computer.
After this issue surfaced last week, Microsoft took the patch off the Critical Updates list and added it to the Recommended Updates list. So you’ll only find it if you choose the option to visit Windows Update and scan your system. Most people will probably be just fine. I’ve got this fix installed on several computers here, all using Norton AntiVirus 2003. Everything’s running normally, with no performance problems at all. But you might not be so lucky, especially if you’re using a different AV program.
If you’ve noticed that your system has slowed down since the last time you updated it, this update could be the cause. To fix the problem, you can remove the update (from Control Panel, choose Add or Remove Programs and then select the “Windows XP Hotfix (SP2) Q811493” entry. You can then wait for the updated patch from Microsoft, which should be ready in a few days.
If your system isn’t displaying these symptoms, however, leave the patch installed!
Ed Bott 
Great info, this problem has been annoying me for a while now, but didn’t know how to fix it.
i can’t uninstall it becasue the remove icon doesn’t show after i click on it
I can’t uninstall it either. The remove icon isn’t shown for it or most of the other hotfixes. Why is this and how can I fix this.
Same problem — I can’t remove it because it doesn’t say “remove.”
Hmmm. Every single one of the hotfixes installed on my computers (production and test) has a Remove option available. The new 811493 hotfix is definitely working properly now… I am personally aware of a problem on computers that are using Diskeeper for defragmenting. Are you guys using Diskeeper?
I previously installed Q815485 hoping my laptop would connect WPA to my router. I then found the toshiba driver update that stated
NOTE:
*When using the Atheros Client Utility for WPA, do not install the Microsoft
Windows XP Support Patch for Wireless Protected Access, Q815485.
This Patch is not needed.
I cannot find Q815485 in add/remove programs OR in System Restore 😦 ??
Is there another way to remove hot “fixes” ?
thanks
The classic treatment for a problem like this is, paradoxically, to reinstall the update you don’t want. Doing so usually adds its uninstall routine to the Registry and allows you to remove it.
However, if you can wait a few weeks for Windows XP SP2 (or install the RC2 version now), your problem should eb solved. Excellent WPA support is built into SP2.