Glen, Follow the instructions below exactly and your problem should be solved.
Right click the shortcut icon for IE next to the Start button, choose Properties, change it from 'normal' to 'maximized'. Now open it.
Now right click any link on the page, choose Open In New Window....don't maximize it....instead, use the mouse to resize it to what you want it to be.
Now close the FIRST window you opened, and then close the new one you just resized.
Reopen IE from the shortcut icon again, and all windows from now on will be the size you chose and created.
Note: If you don't have an IE icon next to the Start button (Quick Launch area) use the shortcut in your Start/Programs/Internet Explorer and follow the instructions above.
Another alternative is to go to the link below and download "IE New Window Maximizer" which is Free.
I use XP Pro, up to date. When I open a new window (right click, open link in new window), it will not open to a full window, only about 2/3 of the screen size. Does anyone know where this 'opening size' varible is stored? I can find no adjustment in Properties so I am guessing that it is in the registry, but where???