By HID, do you mean HPS (=High Pressure Sodium)? Both Metal Halide and HPS are considered HID (=High Intensity Discharge).

Some Sunsystem ballasts will safely operate either type of bulb, provided it is the right power, but it would clearly state that it is switchable. A standard metal halide ballast will not light a standard HPS bulb.

If your ballast is not switchable you can buy an HPS conversion bulb which will run in your ballast and produce an HPS spectrum. HPS conversion bulbs typically have some blue light which is not present in a regular HPS bulb and so appear a slightly different colour but the output is very similar to HPS.

Thanks for the info. Yes I did mean to say HPS. I'm not sure if it is switchable, if not, its encouraging to know that I can buy a conversion bulb. Thanks again.