Try connecting it via VGA (or DVI), if you're currently using mini-HDMI or a DVI to HDMI cable.
I had a similar issue with an ASUS screen, and switching to the VGA cable fixed the problem.

I'll try the VGA cable (I'm using DVI.) Thanks.

The VGA cable won't work. The Nvidia drivers disable fixed aspect ratio scaling when connected to an analog output. Scaling only works with a digital connection like DVI or HDMI.

change the output=surface line

I was going to say this earlier but I wasn't sure......yeah OP set output to ddraw or Direct3D.(case matters here I think)

Dosbox games from GoG generally look just fine on my HD display though, its a 27" I think.

Fullscreen they look just fine and dandy to me. Sometimes the interfaces don't look the best, but its not as much to do with the old graphics as, well, the interface used.

I wish I could afford 27" :P

:\

Suffice it to say I had a good 24 inch 1920x1080 max res. and that died(floor model no warranty) after 2 years so I ditched it for a 22 inch.(Same max res.)....but WITH warranty this time. I know some say store warranties are crap, but I could drop this thing "accidentally" any time within the next year and a half or os and they'd replace it for the warranty fee(20 bucks) which is good.

If all of the games were running fine previously it's no good changing the conf files now as it would seem that the conf files were fine as they are and fixing whatever the problem is would fix all of the games at once.

Like someone in the thread mentioned earlier this could be the result of a video card driver update.

Damn, well I can't work out why it's doing this but I know a way around it.

People who've suggested changing output=surface to output=ddraw are on the right track.
As well as this, you need to change the 'original' in fullresolution=original to your monitor's native resolution.
As an example, mine would be fullscreen=1280x1024.

Keep aspect=true (it's because nearly all DOS games were designed with non-square pixels in mind).

If the fullscreen scaled picture is a bit blurry for your liking and you want sharper pixels, you can change scaler=normal2x to scaler=normal3x.

Did you install a recently-released GOG before you started experiencing this issue? I recall skimming a thread about changes to doxbox configuration for recent GOG releases. Don't know if this would affect all of your dosbox games or just the new one, tho: It's been a while since I've tinkered with dosbox. Someone else here might recall the details.

Yeah. I know a way around the problem, but that's not as satisfying as solving the problem and it requires modifying all the .conf files. =(
Nah, only the new one would be affected. Separate .conf files is the secret to how GOG sets them all up to run with just a desktop shortcut.

In addition to that:
Some monitors let you choose how they should handle resolutions other than their native one (does not apply to CRTs).

Actually, it seems my monitor has aspect ratio correction... if you use a VGA cable. It's disabled if you use HDMI or DVI.

Asus, you make nice monitors, but some of these design choices baffle me.