I need a program that will allow my computer (runs windowsxp pro) to
function a a scientific calculator

Hi, 

The best one I've found is part of the Microsoft PowerToys for Windows XP.
http://www.microsoft.com/windowsxp/downloads/powertoys/xppowertoys.mspx

The Calc toy is very good, allowing Variables, constants, functions,
conversion, and Graphs. Very handy and works well without glitches.

Try it out, if it doesn't work out for you or you need one with a
specific functionality which the Calc doesn't offer, just use the
Clarification Request button and I'll find something else for you.

thanks,

webadept-ga

Ok this Are My Recommendations. All of them are free which means you
can download them totally for free. And they all work on your version
of windows.

-Calc98 5.3
Image: http://www.flow-sim.com/images/calc.gif
Link: http://www.vadino.com/windows/utilities/desktop/calc98.html
Download: http://www.calculator.org/calcw.exe

-Equalizer 1.73 (My Favorite)
Image: http://kobi.virtualplastic.net/eq/ssmach.gif
Link: http://kobi.virtualplastic.net/eq/index.html
Download: http://www.softpedia.com/progDownload/Equalizer-Download-607.html
Note: Full Skinable

Hope This Helped, these are both great programs but I would most
highly recommend Equalizer 1.73.