Changes in Display of windows in XP

When I attempt to move an open window, the window shows as an outline only (it used to show me the whole contents as I moved the area displayed). This means that I cannot see the axact window contents until I release the mouse button. It is confusing because I used to be able to ACCURATELY move a window before letting it rest in position.

Sorry, I don’t know how to explain the problem more clearly.
Hope you can help.
gwr