If all you want to do is make graphs consider trying gnuplot (www.gnuplot.info). It wants data in a plain text file in columns. It's very fast. A week's worth of data from my log file has around 35,000 data points and the graph snaps onto my screen even on my old Toshiba laptop. It has zooming and auto ranging. It isn't the most straight forward thing but if you can program Arduino it shouldn't be too hard.
It even does Windows now.