Fabulous shrinking monitor image

At first I thought it could be the heat (heading for 110 degrees?). After the spectacular failure of the 19-inch Dell CRT monitor, an investment of $30 brought a ancient used monitor of a much more modest size. It's been great, and with a good quality, non-quavery screen, but this morning the image was visibly shrinking in from the sides. I finally found the hidden control panel and made some changes, and all seems to be well. Maybe the heat and some of the electrical activity frizzled something. I'm keeping my fingers crossed because I do not want to be dealing with hardware again any time soon.