Right I've been clicking the option, so can you talk me through how to do it in DOS?
I've not used it for YEARS! The games install in the K drive.

Ok, I'll give it my best shot but I'm not extremely familiar with vista:

Go to start -> run
In the box type "cmd" without quotes and press enter, a dos window should open.

If the default path displayed in not K type "K:" without quotes and press enter.
After this type "cd foldername" without quotes (replace foldername with the name of the folder the game is in).
Once there simply type the name of the file "dg" without quotes and press enter.
Does the game start?

Ah, that's what I was doing wrong, I was doing the K and the CMD the wrong way round.

Anyway, got the same errors, and yeah the resolution's now16 bit colours, 800x600.

ok, let's try this next:
Right click the executable file and select properties, under the "compatibility" tab, enable the "run in compatibility mode" then select windows 98 from the drop down menu.
Apply, close the properties and try to run again from dos... result?

Same result.

uhm...
Let's see if we can force it windowed...

Right click the executable file and make a shortcut to it, rename it into somethin simple (e.g. "windowed"), then right click the shortcut and select properties.
In the "shortcut" tab, add this to the very end of the "target" field (as in, after the ending " ):

-windowed

Apply your changes, and try to run the shortcut you just created from dos...

Put -windowed in general right?