David,
When I run DOS Fractint under DOSBox here, it can change resolutions but DOSBox doesn't allow resizing the window.
I have a 1920x1080 disk video mode set up for DOSFractint that works. Would be nice if DOSFractint allowed me to use a non-disk window that size. :)
You can put any window size you want into fractint.cfg. If it is too big, fractint 'should' send you back to the selection screen. Also, if you rename fractint.cfg to something else (say fractint_old.cfg), then the available window sizes will be auto detected and you can see them using the <DEL> key. It currently won't save a new fractint.cfg file. It is in the works. Write down the suitable window sized, change your fractint.cfg file back, and then edit the entries as needed. Full screen may not work very well because of differences between the actual physical screen size and the allowable area for writing to the screen without drawing on the task bar, etc. Jonathan