In a large saucepan of salted boiling water cook the linguine until it is al dente.
While the linguine is cooking, in a heavy skillet cook the garlic in the butter over moderately low heat, stirring, until it is golden, add the beets, the cream, and the water, and simmer the mixture for 6 minutes, or until the beets are tender.
Stir in the horseradish and salt and pepper to taste, drain the linguine well, and in a bowl toss it with the beet mixture.
Divide the pasta between 2 plates and sprinkle it with the parsley.