It doesn't have anything to do with DirectX version. I guess you're running the games in DosBox under Windows XP. Windows XP has a known problem with using the basic refresh rates of the resolutions for applications/programs, eventhough the refresh rate for the monitor is set in Windows XP to a high value. Might be that they didn't fix that even in new follow-ups of Windows XP - Windows XP 64bit and Windows Vista.
There is a way to help that, though, but it requires you to set some values in the registry which is anything else as recommendable for you as you seem not to know much about computers. But there's a program that sets that for you, only rune it once and it finds the correct resolutions and refresh rates of your monitor out, setting the refresh-rates then to their highest values. In Windows XP AND in applications / programs. You can get the program here -
RefreshForce