Although i do know of some growers who use metal halide from seed to harvest because they claim "they love the bud it produces" i'm the other way round been using hps from seedling and will be until harvest.

Almost the same thing happened to my friend he was looking around his garage (well his mum's) and found 4 250w hortilux growlights with reflector's and ballast. which me him very happy (and me pissed off because because i had just forked out £60 or $120 for a 400w HPS)bastard.

Good luck with growing i am far from the most experienced grower around but i have spent the last six months trying to learn (and succeeding 7oz first grow) everything about growing cannabis.

If it has an e40 fitting you could always add in a better growlight. You may need an MH to HPS conversion bulb depending on ballast.