Try this in TCC v14.02.44: Type OPTION and press Enter. Select the "Advanced" tab. Make any change, or none at all; click on OK. Then try to execute any command followed by an argument. Code: C:\>ver /r TCC 14.02.44 Windows XP [Version 5.1.2600] TCC Build 44 Windows XP Build 2600 Service Pack 3 Registered to Charles Dye - 5 System License C:\>option C:\>ver /r TCC: Unknown command "ver" C:\>set path TCC: Unknown command "set" C:\>echo foo TCC: Unknown command "echo" C:\>dir * TCC: Unknown command "dir" C:\> This is behavior appeared quite recently. I'm pretty sure that build 42 didn't do it. Nor does the current TCC/LE.