How can I make my windows stay full size?

Running Internet Explorer 6 on XP home edition.
I have never in my life tried to shrink a window, much less by a tiny fraction.
But no matter what I do my IE window is full size for about a day and then regresses to being a hair smaller than full size - just enough that when I try to touch the scroll bar it clicks on some window behind and changes the whole screen.
What causes that?
What can be done?

Close all IE windows except one.

Using the handles, drag the corners of a window out to maximum; **do not ** "maximize’ the window with the icon in the upper right corner, or the context menu you get by right clicking on the button in the task bar.

Then, right click on the button in the task bar, and select “Close”. Do not close the window by clicking on the X in the upper right corner.

Open a new IE window. Voilà!

Some applications or websites may reset the window size again however.