XP Pro, SP3, MSE When going to the Microsoft Update site and clicking “Custom”, I am continually being offered two different versions of updates for Root certificates. One is plain Update for Root Certificates, the other is Update for Root Certificates [September 2009] (KB931125)

That’s because MS does not consider it a critical update (go figure) and Root Certificates updates are not offered by AU (go figure). An update’s released every 2-3 months: To get it, you’ll have to run Windows Update manually, do a CUSTOM scan, and then click on the Optional Software updates category to make it available for download.