Ski

Hello, I have an Apollo 8800 PC based DVR system. It is running on Windows XP Professional. What piece of hardware do I need to hook up the RS-485 wires, from my PTZ camera, to the computer? The DVR card itself has no RS-485 inputs, the Diginet software has PTZ options on Com1 and Com2. Should I get a USB RS-485 adapter? Also, will installing Windows XP service pack 2 interfere with the operation of the DVR? Drive C: is not allocatable, it has no recorded data on it.