What are some good / easy-to-use audio sweetening programs to use on a Windows machine?

I got some audio tracks that have some air conditioners in the background, and was hoping for a way to knock down some of that noise. I assume I can't get rid of it, but it'd be great if I could do something to help the audio sound better.

Thanks!

I've had good luck with using Soundbooth directly from the Premiere timeline. If you have some audio of just the AC, you can take a sample of it and tell the SW to eliminate only that sound. Works OK.

take your pick. Soundbooth, Sound Forge, NewBlueFX has a lot of nice stuff and there are a couple of freebies out there. Audicity is one that comes to mind. Pull a SOUND PRINT of the noise only, set it in the program of choice bring the audio into the program, let the program work.
Here's a tip, take a little out at a time otherwise you stand a chance of changing the sound of the voice. Could end up sounding like the speaker is in a big cave OR like Mickey Mouse. Little bites.