Three days later you probably have this solved already, but if you don't:
Remove fixed?
Code:

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DLLFUNC var KillFile(long file) {
	STRING *my_file = (STRING *)file;
	if(remove(my_file->chars)) {
		return _VAR(1);
	} else {
		return _VAR(-1);
	}
}
	//fixed *temp = (fixed *)adll_getwdlobj("temp");
	// temp is a pointer to VECTOR structure with newer SDK?
	VECTOR* vTemp = (VECTOR*) engine_getobj("temp");
	if (vTemp == NULL) { return _VAR(0); }
	vTemp->x = _VAR(3.14f); 

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Alternately, use the SDK packaged with 6.40.5 or 6.50.6 along with the applicable 3DGS version, and this should probably work:
Code:

---

DLLFUNC var KillFile(STRING* _sFile) {
	if (_sFile == NULL
	|| _sFile->chars == NULL
	|| strlen(_sFile->chars) < 1) { 
		return _VAR(0); 
	}
	return _VAR(remove(_sFile->chars));
}

// in C-Script
plugindir = ".";		// place the dll plugin in your project directory "."
							// or set this string to Visual C++ Directory
dllfunction KillFile(_sFile);

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