I'm not sure what plug-in that would be (or your system) but I've gotten good results with programs like Cool Edit Pro (now Adobe Audition). EQ can reduce some types of noises as well as the noise reduction filters in Audition, but others simply can't be removed or even reduced without affecting the stuff you want to keep. M&E can help mask problems too.
The Sony (formerly SF) noise reduction plugin is excellent for removing certain types of background noise. It plugs right into Vegas which makes it very simple to use. I've used it to sucessfully remove HVAC noise and other rumbly stuff.
I"ve heard amazing things about the Waves Restoration Bundle which includes a great plug called X-Noise, but it's fairly pricey.
You can do a lot with equalization to attenuate background noise, but the noise reduction plugin makes it *much* easier and faster.
In a pinch, use the Waves 30-day free trial. If you have ProTools, there's a 30-day free trial of DINR, too... for your next pinch. I haven't used SoundSoap, but it's cheap. In many cases though, EQ turns out to work best...
I have heard of people on here refer to a plug-in or software called SOUNDSOAP that is good for removing unwanted noises and sounds. I am not sure of the link but it might be www.soundsoap.com. If that is not it, just do a google search for sound soap.