I have been trying to get a definitive answer to this question.

I was reading the DIY links that Carmie posted a couple of weeks ago.
I have seen this ATJ's Marine Aquarium Site - DIY - 150W Metal Halide Light (http://www.aquariaforums.com/visit_entry.asp?EntryID=493), before and thought it looks like a cheap east way to light my next 20g project. So....I have a couple of questions.

Will any 500 halogen work light fixture work? The link seems to have been posted somewhere outside the US.

Will any 150 watt ballast work with a watt DE bulb? I was looking at this one BallastWise - HID E-B DXE150HID1 (http://www.ballastwise.com/item.asp?PID=126&FID=17&level=1),

How do you wire a DE bulb? is there one side for hot and one for neutral?

Are the ends on US bulbs compatible with the work light ends? I believe they are rx7's?

I have been looking at this project off and-on-for a couple of months, any body tried it out there?

nope, but you have some serious questions there.

The units components are pretty much fundamentally the same, theres no reason your garage light cant do the job if the correct bulbs are still selected. Even diy set-ups from hydroponic shops are cheaper than asking prices at the LFS.

I can't comment on your specifics as i dont really know the brand of ballast your refering to in the slightest. But if its rated for 150w & uses RX7 ends bulbs, then i suggest you check out something like aquamedic aqualine products for reef specific bulbing.
http://www.swelluk.com/img/shop/full/Aquarium-Lighting-Replacement-Lighting-and-Bulbs-Metal-Halide-Aqua-Medic-aqualine20000.jpg

One of my friends got the lights for his frag setup off of a site that sells stuff that was confiscated from drug dealers. :)

that would most likely be PropertyRoom Auctions Online (http://www.propertyroom.com)

careful, a lot of plant growers go cheap and do the high pressure sodium but you'll see a ton of sunlight supply ballasts that are switchable at amazing prices. If you dont mind used go for it. I've picked up a few things there.