eCalc : Free Windows Calculator
If you are not satisfied with the default Calculator in Windows, then you should definitely give a try to eCalc. It is a nice, little default Calculator replacement and its interface looks very nice. It has got large buttons for easy mouse navigation and large character display that is easy to read. It is a freeware and only 973 Kb in size. It supports Windows 98, ME, 2000, XP and Vista. You can also use the online version if you don’t want to install it.