[redbees]

carpetmojo,

May I suggest that in order to register/make known to Sony your new 350, with your new reader plugged into your computer, you open Sony Reader Library (perhaps as in your first post Reader Library will automatically open when your reader is plugged in), then take the following steps. Go to:

Sony Reader Library > eBook Store > My Account > Manage/Rename Devices

You will find 'eBook Store' listed on the left side of the Reader Library software, below Status and above Computer. Once you are in the Manage Devices section, you ought to be prompted to register the new device.

I'm not able to remember exactly what I did in order register either of my PRS-x50 devices, but this is close. If all else fails, call Sony CS. Good Luck.

ETA: As others have pointed out, the same instance of Reader Library will manage both your readers. I am also assuming you or your son registered/authorized your computer and your 650, and set up an account with Sony -- that seems probable.