newb h.i.d. question

I have a quick question.

I just purchased a light off of craigs list and got home hooked it up, looks like it has a 250w MH bulb in it.. guy said it was a 400w hps setup.. is there any way that a 250w mh conversion bulb would work in the 400w ballast?

the light is clearly blue, and it looks like its got the big e39 mogul socket.. but the bulb looks like conversion bulbs i have seen on line.. its a hydrofarm system, and how can i tell if its 250w or 400w? its not written anywhere. tried to call the guy, he didnt answer. can i just go buy a 400w hps from HD and throw it in there?

let me know, im a cfl'er gone hid.

What Are The Dimensions Of The MH Bulb? Do You Have A Picture? And Make Sure You Know What Type Of Ballast It Is...Don't Try To Run It Or It Could Blow The Bulb...Unless The Guy Sent You A 250W MH Complete.....

after looking more into it.. its an m58 ballast, 250w MH ballast, so i just ordered an EYE 220w HPS conversion bulb for m58 ballast... found it for $49.99..

should do well in a small are.a