Utility to lock window position & size of windows in Windows 7

Try a window manager

http://www.desksoft.com/WindowManager.htm

WindowManager helps you to improve your work flow by remembering and restoring the position and size of your programs and windows. Many programs don't remember their position and size between sessions and even Windows explorer does not always restore windows to their last position. This is where WindowManager steps in and makes sure your windows are placed exactly where you want them every time you open them. WindowManager even allows you to lock the position and size of any window, so that it will always open at the same spot no matter where you move it. The window handling is fully customizable and you can set up special rules for your favorite or most frequently used windows.

If you set the desired window size and position and then hold down Ctrl and click the X in the top right to close the application, then this size and position become the default next time you open the application. With some non-standard applications you may have to do this twice to set it.