ALEX,
The resolution that you can obtain depends upon the interaction between the
capabilities of the graphics card and its drivers and the capabilities of the
monitor.
That is, graphics cards and their drivers are made to produce a certain
range of resolutions. Likewise, a monitor is made to be able to accept a
certain range of resolutions.
Therefore, you need to know what the capabilities are of your graphics card
as well as that of your monitor.
For instance, a LCD monitor is usually made to run best at it so called
native resolution. For example, a 17" LCD monitor typically has a native
resolution or 1280 x 1024, 32 bit. Therefore, a user should set the
resolution to match that requirement. If his graphics card is not capable of
doing this, he should upgrade to a card that can.
It follows, then, that you must know the capabilities and requirements of
your graphics system to be able to settle your issue. Also, graphics card
drivers can become out of date, and updating to the latest drivers can
resolve problems. In order to do this update, you need to know the name
(ATI, nVidia, Intel, etc.) and model number (like ATI 9600 AGP) of you
graphics card.