To be perfectly honest, I don't think you have much chance of anything but a marginal improvement - and it's more likely that you'll end up 'colouring' the sound by removing stuff that really needs to be there...

Parametric EQ may help, as will compression and normalising - all of which SoundForge (my all time favourite programme) has.

4.5 was good, and I've forgotten which bits were missing as I'm on 6 these days... I think it was noise reduction and MP3... nope, can't remember!!

Most important of all, remember to keep the original safe and work ONLY ON A COPY!!