I finally found a way to preserve ginger roots when I buy them. I end up having them go bad every time, because you just can't use all that much of one, so this is a lot less frustrating.

"Scrape and cut into 1/4 inch slices enough non-fibrous young Ginger root to make 1 quart. Put the slices into a large non-aluminum pat and cover generously with water. Bring slowly to the boil an simmer, covered until tender (20 min). Add 1 cup sugar and stir until the mixture boils. Remove from heat.
Cover and let stand overnight at room temperature.
Recook, simmering gently for about 15 min (after coming to the boil). Add 1 seeded sliced lemon and 1 cup light corn syrup. Uncover and simmer 15 minutes longer, stirring occasionally.
Remove from heat and let stand covered overnight.
Bring the mixture to the boil again and add 1 cup sugar and simmer for 30 min STIRRING CONSTANTLY (burns easily). Add 1 cup sugar, bring back to the boil and remove from heat.
Cover and let stand overnight again.
In the fourth cooking, bring the mixture to a boil once more. When the syrup drops heavily from the side of a spoon, and the ginger is translucent, pour the mixture into sterile jars and seal. This yields about 5 cups.
If you want Candied ginger...drain the ginger after the last cooking. Reserve the syrup for flavoring sauces and allow the slices to dry on a sheet or better still a rack, overnight. When well dried, roll in granulated sugar and store in tightly covered glass jars. "