Firefox isn't going to just offer to install an extension unless another program you have installed wants to install an extension for Firefox the next time you boot the PC or the next time Firefox is launched. Do you have anything else from TrendMicro installed on that PC? http://esupport.trendmicro.com/en-us/home/pages/technical-support/1058625.aspx '''''"What is the Trend Micro NSC Firefox Extension?"''''' The Trend Micro NSC Firefox Extension is the Network Security Component that is responsible for the Web Threat Protection of your Titanium program in the Mozilla browser. You really don't need that type of TrendMicro extension; Firefox includes that type of protection.