pmaCalc 

pmaCalc is THE replacement for your pocket calculator. it combines a scientific calculator with a programmer's calculator.
pmacalc is a expression calculator and the replacement for your pocket calculator

PG Calculator (Second Edition) 

PG Calculator is a powerfull scientific calculator and an excellent replacement for standard Windows calculator. It ofers full customizable user inteface and looks like real calculator on user desktop. PG Calculator works Algebraic and RPN modes.
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ESBCalc 

ESBCalc is a Freeware Win32 Scientific Calculator with Infix Notation, Brackets, Scientific Functions, Memory, Paper Trail, Result History List and more. Now includes customising of the Colours used and customising how the Hints (ToolTips) appear.
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ESBCalc Pro 

ESBCalc Pro is a Win32 Scientific Calculator with Infix Notation, Exponential Notation, Printing, Brackets, Scientific Functions, Memory, Paper Trail, Result History List, Hexadecimal Conversion, Fraction Conversion and more. Register once for life.
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A+ Calc 

A+ Calc is a scientific calculator with a multi-line edit display that shows all calculations and allows editing and recalculating equations. A+ Calc includes hexadecimal, statistics, and unit conversion tools, and save and load calcs from files.
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Numero 

Numero is a calculator with some nice features. It has a text box that displays all of expressions and answers that have been calculated, and there is eye candy, such as fading in/out and customizable colors.
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