Can whipping cream left too long in the fridge be used as sour cream?

Whipped cream is heavy cream from cows milk (typically with sugar added) sour cream is the same cream that has slightly fermented - it is sour (like its name) the two are not used together in any recipes for western dishes - but experiment, you might come up with something delicious.

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Sour cream is unlikely to whip up as you would like for the many whipped cream uses that are for adding air to make the dish fluffier along with the sweet cream flavor and creamy texture. However, it can make a great topping just the same.

If you sweeten the sour cream with a little sugar or Splenda, it makes a great topping or dip for fruit (grapes are especially good with this with fresh grated nutmeg added). You can alter with other flavors added, like cinnamon, a dab of lime or lemon zest or juice, cardamom, nutmeg, fresh or ground ginger, etc. This topping is also very good on jello, pumpkin pie, etc. As mentioned in the suggestion above, experimenting can turn out some great new flavors.

Some creamed soups and sauces may suggest adding a little sweet cream (not sweetened) at the end for smooth texture and for flavor. In that use, sour cream works just as well and sometimes better. It will be better if you temper it with a small amount of the soup or sauce before adding it all at once to the dish (to avoid separation/curdling).