What is required to connect a casio keyboard to my computer and record onto my HDD?

[mitchafi]

I'd like to mess around a bit with my keyboard and try my hand at remixing songs. I know the keyboard has a MIDI in and MIDI out but other than that i'm clueless. My sound card is an audigy 2 ZS. I'd also be interested to learn how to do this with my guitar if it is a similar setup. Also, any reccomended software for mixing? I know this isn't the software forums but I don't want to make a new thread over there just for that.