User Account Control of windows 7 asks for your permission before installing software or opening certain kinds of programs that could potentially harm your computer or make it vulnerable to security threats, if you do not want to see that message you must deactivate UAC(User Account Control). If you download Firefox from original/genuine site you do not need to worry. see here for more info: http://windows.microsoft.com/en-US/windows7/Security-checklist-for-Windows-7 http://windows.microsoft.com/en-US/windows7/What-is-User-Account-Control http://windows.microsoft.com/en-US/windows7/What-are-User-Account-Control-settings thank you Please mark "Solved" the answer that really solve the problem, to help others with a similar problem.