Methods of Amplifying Poor Audio from Camcorder Recording?
From your description of the audio, it is going to be hard to fix, as white noise tends to cover a very broad frequency spectrum and so is hard to get rid of without losing what you want to keep.
A decent starting point for you would be to use a freeware audio editing program like Audacity. Here is a noise removal tutorial using Audacity.

You can also use audacity to cut out sections where there is no background talking. Then you can use an effect called a compressor to attempt to raise the level of the speaking to a better level, although you may still find you are amplifying some background noise. Here's a description of the audacity compressor.