HPS on MH ballast

Hi there.
I am new in this forum and i want to ask a question.
I bought HID reflector which came with ballast already build in. On the ballast it says that it is for Metal Halide lamps but it is containing 3 parts like HPS ballasts (transformer, capacitor and something like capacitor but with 3 exits) not like MH ballasts with 2 parts (transformer and capacitor).
I bought one HID light E40 400W and on the cover it says MH but on the light it is written HPS 400w E40 but it emits fairly white-bluish color of light and the inner tube is transparent not like i see in the pictures of HPS white in color.
I was thinking of baying HPS light and use it in this reflector but i am not sure if i would do right.
Can someone help me with this questions?
I can send pictures if it is needed.
If it is MH ballast can i convert it to HPS with using starter for HPS?
Thanks.

I am using a 1000 watt HPS setup with a 1000 watt metal halide bulb for vegging and it works fine. When its time to flower I will swap bulbs. I'm not sure if it will work with a halide setup and a HPS bulb. It will not hurt the bulb to try. As long as you use the correct wattage you should be fine. Dont put a 400 watt in a 1000 watt fixture. It wont work for very long if you do.

thanks man for replaying i will try like you say. i am very pissed off of those merchants here, no one knows what is MH or HPS lights or ballasts, even more they dont know what a ballast is they call the whole ballast (capacitor, transformer and igniter ) just capacitor LOL. for them 400W light i 400W light no mater what light just the wattage to be right. i was asking do you have 400W HPS light bulb and ballasts they say yes we have 400W light bulb. LOL LOL LOL