How are you trying to open them?
Directly by double clicking on a RMC type file?
Or by opening the RootsMagic chart program and using the open command?
If you are double clicking on the chart itself, with the rmc extension, you will probably have to browse through your program list to tell Windows which program to use to open the file.
It will be in the Programs, RootsMagic folder, RMChart.exe.
OR, If you double click on RMChart.exe it should open and you can use File > Open to pick which rmc file you wish to open.
You can even create a new, small, temporary chart from RootsMagic itself and view it, close that chart and open one one you want to use.
======= You are asking about wall charts, aren't you? =======
Yes, I was asking about wall charts, and I went back into my files and tried your suggestion and voila, I am able to open and print! Thank you so much!