Ohhhh! IE! Really? You really SHOULD at least switch to Google Chrome. It's free....and way better! Honest!
My sister was like you...wouldn't use anything other than IE. I even downloaded it all and had it ready....and she only used IE.....until she began having issues and phoned me for help.....and when I asked why she wasn't using the others....well...she tried Google Chrome....and hasn't looked back.
However, to answer your question....
First, close all open IE windows
Launch IE again.
Right-click on any link and choose Open in New Window.
Resize the resulting secondary window to the size you want for all secondary windows.
Now close the window by holding the Shift key and clicking the X icon
in its top-right-hand corner.
Set the remaining window (the original one) to the size you want IE to have when initially launched, and close it in the same way.
This should work.