|Try the monitor with another computer. If you get the same or similar symptoms on the other computer, the problem is with the monitor. |
You could try using the OSD (On Screen Display) feature of the monitor, and setting the settings for it to something other than defaults - the defaults often get out of adjustment as the monitor ages - but often there's nothing you can do that helps enough.
For a CRT monitor, for a given resolution or when you change resolutions in Windows the display may not fill the screen properly - off center, smaller or larger than the screen size. For a particular CRT monitor model, if you use the OSD feature of the monitor to make the display fill the screen properly at each resolution, Windows will retain those proper settings for each resolution after that.
Your physical screen is either a standard legacy 4:3 display ratio (width to height) , or a widescreen display ratio, e.g. 16:9 . Use resolutions that suit the screen.