DVI to VGA splitter

Just wonder: A vendor is using a DVI to VGA splitter to use two monitors one 17″ and one 47″ display. Going from DVI from the back of the pc to two VGA monitors(Windows XP) After shutting down for the night and rebooting the next morning the 2nd monitor is not retaining the resolution settings leaving the signal unusable. You have to go back in and adjust the settings. I am just wondering since it is a splitter and not two separate video cards it Windows is not picking up the second monitor upon boot up.