HKT-04 Sega Katana GD-Writers serve one purpose only, to burn GD-R discs. Those who own one may have once inserted a non-blank GD-ROM and come to the conclusion that they cannot read GD-ROM discs. However, there is a "hidden switch" in the GD-Writer that can enable it to read GD-ROM discs.

Source: http://forums.segakatana.com/viewtopic.php?t=129