In Windows 7 Microsoft has added new capabilities: Mortgage Calculator, Fuel economy and Vehicle lease. To access these features open the Windows calculator then click View, Worksheets, then click the worksheet for the calculation you want.
Under Select the value you want to calculate, click the variable that you want to calculate, then enter the known values in the text boxes and then click Calculate. In the following example we are trying to determine the monthly payment so we enter the purchase price, down payment, term and interest rate.
Don't forget the result will be the monthly payment amount for the actual loan and doesn't include insurance or taxes.
See also Unit Conversion with the Windows 7 Calculator.