I have a dual monitor setup, 1 is an LCD monitor with a refresh rate of 60. The other is an old CRT monitor with a refresh rate of 75. I have an Nvidia GeForce GT 430. My main display which is the LCD is plug into the DVI port of the graphics card using a DVI-to-VGA adapter since my LCD monitor is VGA and the CRT monitor is plug into the VGA port. Can this setup harm my graphics card in anyway?
As long as the monitors are driven at a resolution and refresh rate that is within their specification there should be no problem.
As an example, I am currently driving 2 monitors with a stretched display at 2560x1024 @60Hz and a separate CRT monitor on 1024x768 @70Hz
EDIT: missed off the important bit, all of my monitors are using vga/adapters
I ran 2 different tft monitors for ~1 year on 60 and 70Hz and did not encounter any problems. Thus I assume that there is no problem.