I just installed 4 Hella 500's on my roof rack. The outside two outside lights and the two inside lights each have their own switches. When i went to test the two lights to make sure that they worked only the ouside two worked. I then switched the two leads that ran from the battery to the relay and the inside lights worked. I then switched them back and now none of the lights worked. What could be the problem?

I'd first check my grounds. My Hella 500's gave me a problem b/c I din't realize the switch can only be mounted one direction. The light would come on the switch, but the lights wouldn't come on.

So...
check your sets one at a time.
Check your grounds. If that doesn't work, check the swich to insure it is in the correct position. Check any fuses you have goign to the battery. Is nothing happening? Does the switch light up? Feel free to write and I'll try to help you with some trouble shooting. It's not too hard of a system to figure out. Just don't comlicate it by trying to solve both systems at once, especially if you are sharing a grounding point. (you can get feedback through shared connections.)
John