Did you receive this warning in Firefox or in your operating system? It is important to ensure that you are using a legitimate copy of the Windows operating system that has been activated, via your product key provided with your copy of the Windows CD or on the sticker on your computer. Please try downloading and installing a new copy of Firefox from the [https://www.mozilla.org/en-US/firefox/new/ Mozilla website]. It is possible that you have malicious software or files located on your system. It is highly recommended that you scan for infections on your system using some of the free tools listed in this Mozilla support article: *[[Troubleshoot Firefox issues caused by malware]] Thanks. Let us know if you require further assistance with this issue.