Malware, do not open.

If you did open it, run Malwarebytes Anti-Malware and your choice of other clean-up tools listed here: Troubleshoot Firefox issues caused by malware.

The redirects to the malware distribution sites are believed to be delivered through ad networks on popular sites. You could consider using an extension to block ads, such as: https://addons.mozilla.org/firefox/ad.../ublock-origin/.

Also, see: I found a fake Firefox update.

As a separate issue, your plugins list shows:

• Adobe PDF Plug-In For Firefox and Netscape 11.0.8

That's the August 2014 update level. The latest update is 11.0.20.

Adobe has a fraught relationship with Vista, not wanting you to install -- or apparently update -- Adobe Reader 11. But please try to get current: inside Adobe Reader (or if you have the paid version, Adobe Acrobat) use the Help menu > Check for Updates.

An updater also is available from: http://www.adobe.com/devnet-docs/acrobatetk/tools/ReleaseNotes/11/11.0.20.html