First guess is that you have sync turned on for the Toshiba. So everything that is saved on the cloud and that includes settings, will be duplicated on the Dell. Go to Accounts/Sync your settings and see if sync settings is turned on.
My Dell Inspiron desktop is suddenly displaying the start up page from my Toshiba Laptop.  What have I done to cause this?  I use them independently, not as a network.  But I must have done something accidentally. Dell Inspiron 660s Using Microsoft Windows 10 Home product on both my Dell Inspiron 660s and my Toshiba laptop Since this happened, the desktop has been running extremely slow.
Why is my Dell Inspiron desktop displaying the start up page from my Toshiba 
laptop all of a sudden?