get rid of that old bulb, possible damage to the inner tube from over use can be very hazerdous. I have had them (MH) explode in my grow twice in 8 yrs. There are reports of this regularly on the OGF site.
On the other hand, the fixture is well worth saving.
"the memories of a man in his old age, are the deeds of a man in his prime"
Darn, wish I'd caught this thread earlier... yep, probably a metal halide, not high press. sodium (those are usually cylindrical, like a straight tube). Either 175 or 250w (it would say for sure on the bulb)... not something you could use on top of a glass terrarium, but mass could use it for his pimped out grow area of awesomeness.
In case you were wondering, I can special order this stuff at work tho we don't specialize in "indoor agriculture." I'm NOT one of those closet tomato growers... tho if you've got a closet, you might make a little money on the side