Hi! If DOS complains disk is not there or unreadable, there are tanished switches. Have someone measure two switches for decent low resistance if it's not clean break/make contacts resistances, it is a bit pain of taking it apart and clean those tanish off the silver plated copper plates. Be careful of fine sprung spings and little leaf wiget used to short these two contacts. That is all to it. Saved one like that in Toshiba drives of all kinds, Fixed 4 of them for pc standard and one for T5200/100. Those citizen/Toshiba drives are very rugged for heavy use. Those new Panasonic/Teac/cheapo ones most of time are not up to this kind of much use as I seen so far! Jason D.