Is there any Open source Library to generate and edit .xls and .ppt file?

My task is to extract information from ppt file and compare with another ppt file. I have to use windows platform so i used excel and powerpoint's COM object.

After developing and testing the code in my computer when i exported the file into another computer it just failed. I started to debug in that file, and surprisingly debug was successful from first to last but as soon as click on the executable it fails.

I am totally *ucked up now cause inspite of updating excel dll files into those computers (which will serve the com support) it's not working. In every pc it gives different error message. I don't wanna work COM object anymore. It *ucks.

Can anyone suggest me any open source alternative in which i can read and extract information from Excel and Powerpoint files (both 2003 and 2007 format) ???

My preferred language is c# ........I got an paid solution (aspose) but i don't wanna go for that.

Any help will be appreciated. Just suggest me how can i开发者_StackOverflow中文版 deal with office files assuming ms office is not installed in my computer.

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NPOI works well for Excel; I only know to use the built in, MS object library for PPT files.