There's a virus called "XP Security". I hope you don't have that installed. Removal instructions here if you have: http://www.bleepingcomputer.com/virus-removal/remove-win-7-antispyware-2011 Otherwise, do this:<br><br> #Right click the Internet Explorer icon on your desktop, go to Properties and click the Security tab.<br><br> #Then click the button called '''Reset all zones to default levels'''. See screenshot<br><br> #Click Apply, then OK.<br><br> #Go to [http://www.mozilla.com/en-US/firefox/fx/?ref=logo Download Firefox 4.0.1] and choose "'''Save'''" and save it to your desktop. ''Do not choose "Run"''.<br><br> #Finally, double click the file you downloaded to install Firefox.

See the section titled "Reset system Internet security settings - Windows" at http://kb.mozillazine.org/Unable_to_save_or_download_files#Enable_downloads_blocked_by_Security_Zone_Policy_-_Windows - I recommend using method 2, that will just adjust the Windows settings to allow the download.