WD6CNF 'DSP Filter' works quite well
http://www.hotamateurprograms.com/ It's not clear exactly what you are attempting to do, but this program will take a live audio input and process it, and output to whatever sound device you desire.
One thing to keep in mind if you are using a PC as live DSP, you should have more than one sound device. One to take the input, and one to output the processed audio. USB sound devices are inexpensive. A 'full duplex' sound card will in some cases, depending on what you are doing, suffice. Still good to have a secondary card though.
Your mileage may vary depending on what sort of onboard sound device you have. Laptop manufacturers of late hamstrung us by taking away the 'Stereo Mix' or 'WhatUHear' option from the record sound panel.
I recommend finding a SoundBlaster Audigy USB or similar as your secondary device. Also, take a look at VB Cable software to route audio around the digital domain.