If you have a SoundBlaster card, you could use the free Vienna soundfont creator to make specific samples on specific keys.
Or you could use a higher-end sampler program like Gigastudio.
Search around the web and you could probably find some free sampler programs to use, too. Computer Music (www.computermusic.co.uk) is giving away one (VST SR-202 sampler) which is primarily designated as a drum sampler but can use any .wav file triggered by MIDI.
but primarily you should be able to find a sampler that does this as a vst on a seprate audio track