i have a phillips 400 watt mh bulb with these specs:

Bulb Category : HID
Energy Star Compliant : False
Life : 10000 Hr.
Maximum Bulb Wattage : 400
Voltage : 135 Volts
Watts : 400 Watts

now, seeing as how i have a low budget, i have to buy a ballast kit. this is the one im thinking of:
http://www.businesslights.com/400w-venture...t-kit-p-50.html

i'm not too sure how ballasts work, but i do know that they beef up the voltage in your household wall plug into a voltage suitable for the light you're using...

so if i buy that ballast, will i simply have to get an extension cord and plug it into the ballast and then run it into the wall after i plug it into my reflector/set it up?

You don't give the model number of the lamp, so I can't say for certain that you have the right ballast.
If your lamp documentation specified an M59 ballast, however, then I guess you do.

The ballast you listed is a quad-tap ballast. This means that it can be used internationally with either 120v, 208v, 240v or 277v. If you live in North America, you'll only be using the 120v. You'll want to cap off the other input voltage wires with wire nuts. So, from your line coming in, you'll run the hot to the 120v line (you'll connect the two wires with wire nuts). Your common (negative or neutral) wire will connect to the ballast's common wire (it should say Com on the wire). It looks like that ballast only needs a capacitor, so there will be a black & white striped wire coming from the ballast. You'll connect that to the black & white wire coming from the Cap. There should also be a red wire coming from the Cap. You connect the red wire to one of the wires coming from the lamp's Mogul Base. The other common wire from the ballast connects to the other wire from your lamp's Mogul Base.

You should have a label on the ballast with a wiring diagram showing how to wire it, like below:

There are different types of ballasts for 400W HID lamps.

S51 ballasts are actually for HPS (High Pressure Sodium) lamps, which are way too yellow, however there are conversion lamps like the Ushio S400DD which use this ballast.

M159 ballasts are for probe-start MH lamps.

M59 ballasts are for pulse-start MH lamps. This is the most common as far as I've seen, and is the one that the LL 6500K T15 lamp uses.

Magnetic ballasts are relatively inexpensive, and aside from being bulkier and heavier work very well.

Edit: Quasi-mojo's diagram is of a multi-tap M59 type ballast. This ballast can take 120, 208, 240, or 277VAC in 50 or 60Hz and fire the lamp from it. It's not the 135V that's hard to produce for the lamp, it's the several kV pulse which gets the lamp started which is the reason that you really need the ballast.

wow, thanks guys! i really appreciate it.

I can't seem to find the spec sheet for that lamp. Is there any other writing on the lamp, itself?

You can look for the spec sheet on the Philips website: http://www.nam.lighting.philips.com/us/ecatalog/tds.php
They seem to list a few 400 Watt ED-28 lamps.

278622 400 Watt ED-28 Metal Halide Lamp (Clear) seems to be the one, near the bottom of the page.

thanks for all the help