Your using Windows 98? Reading other posts it seems you dont need DosBox, you can just use the command prompt:
Start > Run > cmd
Some people with Win 98 SE use DosBox, but if the game doesn't work in the command prompt then state what game you are trying to play, maybe its an issue with that.
If you think you do need DosBox and have wrecked your config file, easiest option is to redownload DosBox... the default config settings are okay for most games, tweaking them is just for fine tuning
k: