Latency issue with a Casio LK35

Hi guys,
I'm new here so forgive me if this topic has been broached before.
We have a Casio LK35 keyboard here (the lighted-key model) midi-ed up to a PC containing an M-audio Delta soundcard. The latency time is unusably long. I have tried running on both the PC's native ASIO drivers and those of the Delta, but no real change. Have also tried resetting buffer sizes and changing prefs in the Delta control panel, but no joy.
Any ideas, anyone?
Thanking you in advance.....

Are you trying to record, or just play ...using your computer's sound card?
Usually the time delay is from using a 'soft synth' set of sounds. The delay is because the computer has to generate the tones using the CPU power. Most cards have a 'built in' sound set, that is not using the CPU. Those tones may not be as 'nice'...but will track with your playing, right on time. I'm not familiar with your soundcard...but with my SoundBlaster Live....there isn't any delay, even using the Soundfonts or the 'on card' synth.
also, make sure you aren't creating a 'data loop'...that is sort of like feedback. Looping the midi in ,to the midi thru, to the midi out. The simplist way to eliminate this is to unplug the Casio 'midi in' plug