I've never heard of a "premium" installer and it's definitely nothing that Mozilla uses, so it's likely you have some malware on your machine.

• Uninstall Firefox
• Scan for Malware, Troubleshoot Firefox issues caused by malware
• Reinstall Firefox by going to www.getfirefox.com and downloading from there

Definitely bogus. Someone over at MozillaZine reported this yesterday. See: http://forums.mozillazine.org/viewtopic.php?f=38&t=2774195 virus: fake firefox update

Quote:
Just now, when I opened firefox, a dialog appears indicating my firefox browser is out of date and ask me to click ACCEPT to update. I clicked and then a file 'Updater_Setup.exe' is downloaded and saved. I run the file trying to update. The what happens is completely different from my previous firefox updates. when I run the downloaded file, a dialog appears indicating a program 'Premium Installer' by TINY INSTALLER is going to run; I click run, then a dialog saying " thank you for choosing our software" I click get started, it comes out another dialog indicating "Express Install 'you are less than 30 seconds away!". I continued, the SW seems trying to install a serial of tools such as Mixi Dj. Definitely, this is not a firefox update. I am wondering whether this Updater_Setup.exe is a virus, malware? Thanks

Be sure to scan your computer for malware or seek help in a forum specializing in malware removal - see Troubleshoot Firefox issues caused by malware for recommendations.