Initially published 2010/03/18; updated 2013/05/01 to edit title in a poor-man's SEO effort
So ... ignoring the whole I'm actually installing Windows thing for a moment, in order to look at some software I'm installing Windows XP (XP because apparently I bought something that came with a license for it) in a virtual machine.
So I installed XP and then upgraded to service pack 3 via Windows Update. It seemed like the right thing to do. Meanwhile, Windows is complaining about my not having antivirus software installed.
I find something called Microsoft Security Essentials that can be installed for free, but it keeps failing with error code 0x8004ff01. There's a link that can be clicked for help, but no help is to be found by following it. The site even provides a search box but it knows nothing about the error code.
I figure maybe if I installed IE8 it would pull in whatever was hip and cool, but no such luck - the same error continues to manifest itself. While searching around on the web for how to solve this I find all sort of abstruse instructions involving editing the registry and rebooting a dozen times. Ahh, Windows, how I never missed you.
However, using the gray stuff in my head (aka: taking a SWAG) I found the the answer is relatively straightforward: Download MSI 4.5 (the Windows Installer), which can be retrieved from here: http://www.microsoft.com/downloads/details.aspx?FamilyId=5A58B56F-60B6-4412-95B9-54D056D6F9F4&displaylang=en
Clicky-clicky and away you go. Your Windows XP with Service Pack 3 (SP3) gets a fancy new icon in the system tray, the antivirus warning icon goes away, and your computer is apparently suitably inoculated for travel to the internets.