The Vivitar 2000 has a high sync voltage that could damage the circuits in your D200. As Anthony wrote above, you will have to isolate the Flash unit from the camera using a Wein Safe-Sync. The Safe-Sync model SSHSHS ($49.20) will mount in the cameras hotshoe and you can place the Vivitar flash in the Safe-Sync's shoe or attach it via a PC cord.
Given the price of the Safe-Sync and the low power of the Vivitar 2000 you might be better off buying a used Nikon SB-24 or similar. Like the Vivitar 2000 you will be limited to Non-TTL Auto flash mode or Manual flash mode. For the most consistant results, use Manual exposure mode and Manual ISO.