Airfont is a soundfont. A soundfont is basically a file (.DLS or .SF2 are the most used) that assigns the different MIDI instrument patches some samples (most of the time they're synthesized samples). What do you use for a MIDI editor and do you use its default sound? And... a creative card from the 90s? Are you currently rocking an Audigy, Live, or.. an AWE based model? Try buying a decent soundcard with good native support for ASIO. I'm currently using an Asus Xonar DX which has native support for ASIO, but I don't really use that feature since all my MIDI notes are hand-clicked in a MIDI editor rather than recorded from an external MIDI device.