I *think* this is the USB driver for the early NetMD units, including the MDS-JB980. I am not 100% certain which units it supports, as I have only the 980 (it definitely supports that!).
Anyone with an MZ-RH1 or MZ-M200 will have problems uploading on that portable after installing this driver. In fact you need to take the first steps outlined in the first post of this thread post "Solution to slow SP upload".