You need to modify the security on the file itself or the folder where dosbox.conf resides.

You can either give "Users" full permission or you can add your own logon to the file or directory and give it full permissions.

Thank you very much for the reply.

I can change the config file, but the games are still stretched all the way to fit the screen when I choose full screen (even though aspect=true). Also, the colors are messed up:

Any idea on what's up (note: this snapshot looks like it's the correct aspect ratio; it was taken when I had DosBox in full screen. What was displayed on the monitor was this same image, but stretched to 16:10)? In in the graphic options part of Vista, I have set my display settings to "Maintain Aspect Ratio," but the games are still stretched.

EDIT: I changed the "fullresolution" option to a 4:3 resolution and now it seems to work just fine. The graphics are still occasionally messed up as above, and for some reason there's a pretty big black border around the whole screen (even though I'm doing 1280x1024 on a 1680x1050 monitor; I'd expect the screen to be filled nearly entirely vertically, but it's far from that). For some reason, when I choose 640x480, the screen is stretched all the way. What's going on?

Also, sometimes none of my keys work except the space key (I have to hit switch either to windowed and back to fullscreen, or vice versa, to fix it).

Set 1680x1050 as fullresolution, this should always show correct AR.

That seems to work somewhat well (though there's still a border for some reason; I've been trying to get the image as large as possible while still retaining the 4:3 ratio). Unfortunately, the graphics are still messed up in full screen:

I can actually see "Tyrian 2000," but for some reason it didn't show in this picture. But, basically, the graphics turn these funky colors when I go full screen (sometimes everything's perfect when I turn to fullscreen, but then I start scrolling through the options and the space that I scroll through turns this funky color).