Return fire is a Windows game, therefore DosBox cannot be used with it.

The only problem I've had with Return Fire is that it would complain about 256 colors, which I fixed by using compatibility mode.

So...try compatibility mode.

Compatibility mode provides an environment for running programs that more closely reflects the behavior of either Microsoft Wind […]
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Compatibility mode provides an environment for running programs that more closely reflects the behavior of either Microsoft Windows 95 or Microsoft Windows NT 4.0. These modes resolve several of the most common issues that prohibit older programs from working correctly with Windows 2000. Programs that experience issues after migration may benefit from being started in one of these compatibility environments.

1. Log on as Administrator,
2. Click Start, and then click Run,
3. In the Open box, type the following command, and then click OK, where %SystemRoot% is the drive and folder in which Windows 2000 is installed:
regsvr32 %systemroot%\apppatch\slayerui.dll

Administrators can use a program shortcut to set the compatibility mode for a target program. This requires that the Compatibility-mode properties be correctly installed and registered on the computer by using the previous steps. To enable Compatibility mode by using a program shortcut:

1. Log on as Administrator,
2. Right-click the shortcut, and then click Properties,
3. Click the Compatibility tab. This tab appears only if the Compatibility-mode interface has been properly enabled on the computer,
4. Click to select the Run in Compatibility Mode check box to enable Compatibility-mode support for the program,
5. Click either Windows 95 or Windows NT 4.0 compatibility mode in the drop-down box,
6. Click OK to save the changes,
7. Double-click the shortcut to run the program.

Okay, I found this on about how to run compatibility mode. I did it all up to the "compatibility tab" part, and everything up to there worked fine, but I cannot find any compatibility tab in the shortcut properties 😖.

Then you didn't follow step 3:
3. In the Open box, type the following command, and then click OK, where %SystemRoot% is the drive and folder in which Windows 2000 is installed:
regsvr32 %systemroot%\apppatch\slayerui.dll

I did. I entered "regsvr32 C:\WINNT\apppatch\slayerui.dll" into the Open box and clicked OK, and it confirmed this by saying it succeeded.

Okay, so I got it - I just created another shortcut and it worked, sorry.

Moving to Windows.

Mirek