Mouse Dust

double triggering buttons can be remedied by soldering in new microswitches. spurious keypresses like you described can have several causes: Bad power supply, broken cable, wireless interference(bursts, far apart), broken usb interface, dirt, failed controller.

The interference you can try to counter with a ferrite on the cable.

If you think it's the usb on the mainboard, use a different USB socket (there was that acer laptop which had some USB ports on a separate board, and if you put your hand near the hinge the plug(internal) would come loose intermittently).

maybe change the cable.

perhaps clean the mouse(the circuit board).

If that won't help, you can only trash it...

Have a look at Evil-Bay. There are many "MS Notebook Mouse 3000" listed, though most seem to be wireless. With some patience, the one you want will likely show up in a few months.

Regards, Tim

So you may as well get inside and maybe the optical encoderdisc is partly out of a bearing, pot is worn, something loose, fluff etc

If only it were that simple! I've fixed mice, with bad microswitches (usually dirty, and some cycles of HV switching burn away the crud), and with fluff in the optical path, and with film on the contact wires, and with...well, basically fingerprints many microns deep all over the rotating parts.

My favorite mice now, though, are all welded closed. Can't get in.

Dremel to get it apart, Tenax to put it together. Won't look pretty but what have you got to lose?