hello
there is an easy explanation....
when the arduino sends some charaters back to the computer at certain speeds that stupid windows thinks you just plugged in a "MIcrosoft Ballpoint serial mouse" which was last sold probably in 1992... every character sent by arduino gets interpreted as mouse movements...
so you have to make your way to the "Control Panel" / System / Hardware and disable the driver... if you delete it , it will come back...
so just disable it...
it's a pain in the ass but windows is stupid and there is only one solution... upgrade to a mac

massimo