Error message from Windows: A disk or memory error occurred.

This is a very vague message from Windows. We know of one case where it happens with Prism 7 Windows.  You'll see that message when you try to do something with grouped scatter graphs (delete graphs, relabel axis, change colors of the points, duplicate the graph) with thousand(s) of data points without replicates. This only happens with grouped graphs plotting individual values without replicates. We'll fix for Prism 8. 

The workaround is to plot column scatter graphs, rather than grouped scatter graphs. Another workaround would be to enter data into multiple subcolumns if that works for your purpose.