then again i'm not positive it's a mv lamp, i was looking for things to identify if it is a hps or mh.
Dude, I went to a demolition site where they are bringing down a manufacturing plant, and bought some 400w MH and HPS High Bay lights complete with reflectors, just as you described. They had 1000w HPS as well. There will be a "tag" of some sort on the ballast that will give you the manufacturer, bulb type, wattage, etc. You cannot use an HPS bulb with a MH ballast and vice versa. They DO make a "conversion" HPS bulb that emulates the "blue" MH spectrum for HPS ballasts.
You will have to separate the bulb/reflector from the ballast housing (simple enough), but other than that they seem to be working great for me. You'll find that if the fixture was used indoors for working light, it's most probably MH (easier light on the eyes), if used for outdoor lighting, it's most probably HPS.
If its a MH, and it has a bulb already,
REPLACE IT WITH NEW!!! The MH bulbs have a protective coating on the inside that filters the high intensity UVA. If thats broken, and it most probably is, it will FUCK YOU UP!! Use sense, don't cheap out, and get a new bulb. You saved enough on the fixture to justify one!!!
Peace