Is it for Adobe Flash? If it is, you do need to close Firefox to complete the installation. It's a plug-in for Firefox.

You can download directly from the Adobe site instead of using the pop-up, if you wish; your decision. See below You have 2 Adobe products that need to be updated: *Adobe PDF Plug-In For Firefox and Netscape *Shockwave Flash 10.2 r152 #'''''Check your plugin versions''''' on either of the following links': #*http://www.mozilla.com/en-US/plugincheck/ #*https://www-trunk.stage.mozilla.com/en-US/plugincheck/ #*'''Note: plugin check page does not have information on all plugin versions''' #'''Update Adobe Reader (PDF plugin):''' #*From within your existing Adobe Reader ('''<u>if you have it already installed</u>'''): #**Open the Adobe Reader program from your Programs list #**Click Help > Check for Updates #**Follow the prompts for updating #**If this method works for you, skip the "Download complete installer" section below and proceed to "After the installation" below #*Download complete installer ('''if you do <u>NOT</u> have Adobe Reader installed'''): #**SAVE the installer to your hard drive (save to your Desktop so that you can find it after the download). Exit/Close Firefox. Run the installer you just downloaded. #**Use either of the links below: #***https://support.mozilla.com/en-US/kb/Using+the+Adobe+Reader+plugin+with+Firefox ''(click on "Installing and updating Adobe Reader")'' #***''<u>Also see Download link</u>''': http://get.adobe.com/reader/otherversions/ #*After the installation, start Firefox and check your version again. #'''Update the [[Managing the Flash plugin|Flash]] plugin''' to the latest version. #*Download and SAVE to your Desktop so you can find the installer later #*If you do not have the current version, click on the "Player Download Center" link on the "'''Download and information'''" or "'''Download Manual installers'''" below #*After download is complete, exit Firefox #*Click on the installer you just downloaded and install #**Windows 7 and Vista: may need to right-click the installer and choose "Run as Administrator" #*Start Firefox and check your version again or test the installation by going back to the download link below #*'''Download and information''': http://www.adobe.com/software/flash/about/ #**Use Firefox to go to the above site to update the Firefox plugin (will also install plugin for most other browsers; except IE) #**Use IE to go to the above site to update the IE ActiveX #*'''Download Manual installers'''. #**http://kb2.adobe.com/cps/191/tn_19166.html#main_ManualInstaller #**Note separate links for: #***Plugin for Firefox and most other browsers #***ActiveX for IE