@nikhils, I reviewed the article on the Sophos website and the Microsoft article linked therein. They refer to Windows security update KB2918614 and this MS article displays the dozens of Windows OS products this applies to, and Windows XP is not included. I looked at my Windows Updates service to determine which updates have been applied to my XP and KB2918614 is not listed. In the MS article it gives instructions for modifying the registry, provided you know the ProductCode per the MSI log, but my XP virtually has no such logs so I don't know what the ProductCode value is for the Firefox installation. Perhaps there are similar articles regarding XP, but I suspect this is an issue that MS is not supporting for XP. Thank you for the effort.