Don't want to make a big thing of this.
This has nothing to do with the monitor or display settings in the computer - it is specific to MACH3 only.
Does not matter what screen set is used - the default 1024 or machblue or whatever - have made no changes to the screen.
The first shot is what I see with the screen NOT maximised, the second when it is maximised.
Also, when maximised, the right hand border behaves like a program internal border - i.e. if the mouse is positioned over it you get the >||< cursor, not the double arrow. If you try to move the border to the left, it shows the position it will go to like it's going to move, but does not move when the mouse is released.
You can also see how there is wasted space to the right and bottom of the screen when maximised.
Maybe it is some Video driver incompatibility with the way MACH3 draws the screen. The machine is isolated. May have to move to where I can hook it up to the net to see if there are later drivers that might fix the problem.
Video is on-board - ATI Radeon Xpress 200 series, Drivers are ATI ver 6.14.10.various.
No other program in the machine behaves this way - microsoft or other.