you need a midi interface. it might be worth spending some money on a decent soundcard that comes with an built in midi interface, i went for the native instruments audio kontrol 1 recently. if your using a desktop there are literally 100's of decent cards you can get.
stock soundblaster cards dont have midi i/o i dont think.
you can find a cheap midi interface for under $100. all you really need is 1 in and 1 out but if you want a cheap interface, i recommend getting at least a 2x2 (2 in and 2 out).