The old amnesia bug,
IE is notorious for this, and there is a fix.......here goes:
1. Close all open Internet Explorer windows.
2. Now, open just one IE window, and press "Shift" while "Clicking" any link to open a secondary window.
3. Adjust the secondary window to the size you want for all secondary windows.
4. Then close it by holding "Shift" while "Clicking" the X icon at top right.
5. Size the primary window and close it in the same way.
You may need to repeat this process if IE forgets after a while.
you can do the same for Windows Explorer, omitting the secondary window
Hope this helps