Generic comment #2:

If you run WinXP or Vista, it's pretty much essential that you get Microsoft's security updates regularly, and getting them automatically is highly recommended. Many people were put off by problems with some earlier updates that caused difficulties for some people, but once you've got WinXP up to SP2, or Vista at any level, I haven't heard of any updates that have crashed a significant number of people.

While automatic updates with automatic install of critical ones possibly does have some "risk factor," the offsetting argument is that for any problems with an update it likely will be very obvious where the problem came from. You won't need to go searching the web (very far) to identify it, and Microsoft support for problems with updates is free. (Even if it is about the only kind of free support you can get from Microsoft.)

Each automatic update runs Microsoft's "Malware Remover" and while the MMR doesn't check everything it does check for "common problems of all kinds" for anything common enough to cause problems for a significant number of users. I consider it worthwhile to let it run at the monthly downloads, but if you "download but decide for yourself whether to install" it may not (or it may?) run every time there's an update.

If you have a problem, you don't have to wait for a scheduled download. You can go to the update site and run the Remover from the site or download it to run manually.

Reports during the last week or so indicate that the MMR was recently updated to remove two fairly significant worms of exactly the kind being described in this thread, although I don't know if those two were exactly the one(s) here.

John