Since you said 27 inches, and that is not a common dimension for LCD monitors, I am assuming you have a CRT (Cathode Ray Tube) monitor. CRT usually have a width adjustment. Look for that. If you had told us what brand and model of monitor you have, someone here could give more specific detail.
It isn't resolution that is your problem. The resolution pretty much only defines how many dots will be used to put across and up/down your lit-up area of the screen.
For example, if your screen only has 20 inches illuminated across the display, changing resolution from 640 or 1024 or 1280 or 1440 or 1680 or 1920 or even 2560 only sets that to how many dots across those 20 inches.
(Side note: sure there may be some fluctuation a bit on the width, it usually will not be a consistent 20 inches - if that, but it should be there-abouts.)
Instead, I would suggest that you look for some monitor adjustment to expand out your lit-up area to the full width.
I can't get vista to display fully on my 27in monitor. Does anyone know of the correct resolution setting, and how to obtain that setting to fill my screen?
27 in monitor, using blue cable (not dvi)
geforce 8500 gt video card (with latest drivers installed)
thanks for all the help!