Try download SonicStage v3.4 available here - http://www.sony.jp/products/overseas/contents/support/download/e_jeb_SS34ug.html
SonicStage v3.4 can be used to convert mp3 to ATRAC3+ and then download into the NetMD. Also included is SimpleBurner, which can convert a CD straight to ATRAC3+ and download into NetMD.
Hope this helps
EDIT: Just realised this is a Sharp MD unit - SonicStage might not recognize it
Hmm I don't think you need 驅動程式, since if it works properly, then the SonicStage should recognize your NetMD upon connection via USB cable. I know the Sony Hi-MD does not have any 驅動程式, but don't know if that's the case for Sharp NetMD
If you mean that you would like to use it as a usb thumb drive, then I don't think that is possible since only Hi-MD supports that format.
If the recording is not loud enough, try using Manual Gain control (default is Auto Gain Control - AGC I think). The specifics should be in the manual, which is available online
EDIT: I just looked up on the MT880, and you can change the recording level (louder or quieter) by pressing |<< and >>| buttons. Here's some instructions - http://www.minidisc.org/brian_youn/immt880/page2.html
EDIT2: I have found the driver for the MT880. Just install it before installing SonicStage, and it will work. Here - http://forums.minidisc.org/downloads/details.php?file=6 You will need to register to download the program however. You might want to uninstall the current SonicStage first, and download the offline installation from here - http://forums.minidisc.org/downloads/details.php?file=21 It is actually quite simple to use, and you can now upload your recording into the computer via USB, which is easy to edit and burn into CD.