If the game is not a DOS game,it will not work in a DOS environment at all.
What I would do if I were you is to find drivers for your hardware which are compatible with Windows 98 OS and then install Windows 98 to other HDD and then install the drivers and simply run the game on it.
But if you cannot get Windows 98 disk or cannot find any hardware supported by Windows 98 OS or cannot find the appropriate drivers,there are always other ways to run that old game.
Just curious...what compatibility modes have you tried?
By the way if you set the compatibility mode for a wrong file,it is logical that the game won't run.For example you must NOT set the compatibility mode for the game's shortcut.Instead you must find a target for the REAL file and set the compatibility for THAT file and NOT the shortcut.Also be sure that the file for which you set the compatibility mode for is the CORRECT file which actually IS a game.Because some games have 2 different type of files.First one is a menu from which you actually click a button to PLAY the game and once you have clicked the button to play the game,COMPLETELY OTHER file is run and that OTHER file is actually a game while the previous one for which you probably set the compatibility mode for is NOT the game...and instead it is the simple MENU from which you run the game.Games like Star Wars dark forces 2 from 1995. which are designed also for Windows 95 OS are a good example of these.
If you do not know on what exactly I mean,you can always send me a copy of that old game for Windows 95 and I will attempt to find a way to run it and once I did,I will let you know how you can run it under your Windows OS.
Cheers!