Did the discoloration begin as a yellowish/green color, then progress to brown? If so, it isn't fungus, but a Pseudomonas Bacterial infection. Fungus feeds off the proteins in the nail plate which is evidenced by nail plate lifting and evident debris in the area of lift. Fungal nails do not turn brown, but will become yellow and dull.
Pseudomonas, on the other hand, is characterized by a yellow/green discoloration; as it worsens, it will go through the stages of darker green, then brown, then black. the darker the color, the deeper into the nail plate layers the bacteria has traveled. If it is indeed pseudomonas, applying the ointments and vinegar to the nail will only give the bacteria the food and moisture it needs to grow. Instead, keep the nail clean and dry - this will remove the moisture from the nail that the bacteria needs to grow, and will actually 'kill' it within a few days. The stain, which is composed mostly of iron compounds, will remain and grow out with the nail plate.
You might want to visit my approved website to see a photograph of a Pseusomonas Bacteria infection. The address is: [url="http://www.hooked-on-nails.com/naildisorders.html"]http://www.hooked-on-nails.com/naildisorders.html[/url]
There is also a picture of a fungal nail.