SteveGG wrote:

Depending on the circumstance and app, my M$ mouse sometimes gets
"jumpy". How to eliminate this ?!

Clean it. Use a penlight to look inside the recess for the LED. Could
be there are hairs or lint in there. Just takes one to flutter around
to make the mouse think it is moving.

Wired or wireless? You gave no model number, just a brand. If wired,
after long time [ab]use, the wires can break but they make erratic
contact when the cord is flexed. If wireless, did you yet replace its
batteries? You've given NO information about what you already tried.

If wireless, is the USB transceiver dongle in a USB port on the front or
back of the case? Have you tried a different USB port? Do you have
nearby RF devices that might interfere with the RF for the wireless
mouse, like a cordless phone, cell phone, or microwave?

If wired, have you disconnected other USB devices (other than the
keyboard if not PS/2) to make sure those aren't interferring with a
USB-attached mouse?

Go into Control Panel, mouse applet, to disable acceleration and reset
to defaults for tracking speed. Retest to see if mouse is smooth. If
so, then reconfigure the mouse settings how you like.

Are you using the generic driver in Windows for the mouse? Again, you
give no information so no idea if you attached a PS/2 or USB mouse. A
PS/2 mouse will show as such while a USB mouse will show as HID (Human
Input Device) when you look in Device Manager (devmgmt.msc). Are you
using a mouse driver that did not come embedded in Windows (the generic
PS/2 or HID drivers or one of the included 3rd party drivers), or did
you install some mouse software to add functionality to the unidentified
Microsoft mouse?