And is there any way to stop this?

Thanks so much

Not on Windows, no. The accepted practice is to not use Maximize, but rather Resize to Fit.

I think it's just how the Windows OS handles new windows.

You may be able work around this in a couple ways...

Use the script step Adjust Window[Maximize] immediately after calling the New Window[]. Or you can capture the window height and width in variables and make a new window with those settings.

I don't have a Windows machine nearby so can't test either of those ideas.

Thanks a million. Your ideas worked perfectly. ******* Windows!