Severe noise reduction how-to
 

I have a tape of which the first 30 minutes are cursed by severe audio noise. In some scenes the noise is pretty bad (Attachment 14249), in others there is a milder version of the same noise. The rest of the tape has no noise.

Ideally, I export the WAV from my lossless AVI, import the WAV in noise reduction software, reduce the noise on a per-scene basis, and export the WAV entirely so I can replace the old audio in VirtualDub.

What software is best for this? Is (the latest) Sound Forge still the way to go? Or have better solutions surpassed it?

Also, any ideas of what caused this noise?