Mix 1/2 cup vinegar and 1/2 cup water and pour over the old urine. If this amount doesn't cover the urine stain, double it.~ Blot up the vinegar solution with paper towels by standing it on it to pull all of the moisture out.
~ Sprinkle the stain with baking soda.
~ Mix 1/4 cup hydrogen peroxide with 1 tsp. liquid dish soap and spread it over the area. Use a stiff, bristle brush to work it into the carpet. Note: (Be sure to test on an inconspicuous place first)
~ Vacuum up the cleaner residue when it is dry. This will usually take overnight. Point a fan at it to speed drying.
