DB-9 and Cat-5

I just received my Slink-e and I am setting it up for the first time. My PC is far from my CD changers. My plan is to use Cat-5 wire and put some DB-9 connectors on it so I can run about 50 feet of wire. Anybody know how the connectors should be wired? I have Cat-5 with 4 pairs. Do I , instead, need to find Cat-5 with at least 1 more wire? I don't know if all 9 pins are used. If not, which ones are? The last question would be - do I wire each pin positionally or do some positions criss cross?