Try "MalwareBytes" to start cleaning up your system:
http://www.malwarebytes.org/
(free version has no "real-time" shield)
You may have to re-set your homepage, and remove the Bing engine (done from the drop menu in the "Search"slot> manage search engines> highlite Bing> Remove> OK.
The following tips help, but methods ("vectors") are dynamic.
FIREFOX: Tools> Options> Privacy> top drop menu set to "Firefox will use custom settings..."> Check 'Accept Cookies from sites'
►Un-Check 'Accept 3rd Party cookies'.
A good collection of effective add-on's (Official Mozilla) is here:
https://addons.mozilla.org/collections/dunbar-pappy/dunbarpappy/
AdBlock Plus (with 'subscription' added) & "Better Privacy" also help defray rubbish.
►► At minimum, get the #1 item for malware prevention: NoScript, which constrains automagically fetching & deployment of tainted assets.
[see this page for how it works, and how to use it...very simple; http://noscript.net/features#contentblocking