There was a great article about noise removal in DV magazine a while back, which covered all sorts of interesting ways to handle it. I've thrown out that issue, though, sorry.

Anyway, as you've discovered, trying to EQ out a noise throws the baby out with the bathwater. So don't use an EQ to remove noise.

Among the other noise removal techniques is the aforementioned "learn and subtract" filter, where you feed the software a sample of JUST the noise and it goes through and subtracts that from the rest of the recording.

Almost all sound-editing programs should have a subtraction filter like this already in them, including Sound Forge. You probably just haven't found it in the menus yet.

You'll find that these filters can sometimes produce other artifcacts, though, so be careful with them and preview any edits and play with the settings. Different programs are going to be better at noise subtraction than others. The good ones are expensive and use a lot of proprietary code to get the job done.