Your old login based on your email address and password should work fine. You then add the reformatted PC as a new device and install the Reader. Since the Reader is already ctivated to that account you will have a total of three (3) devices out of seven (7) maximum devices connected. Then Sony support can deactivate the old PC profile. All of your purchased content should be there available for download again. This is how it is supposed to work. Your mileage may vary.
I have the CONECT software loaded on two (2) machines with one (1) Reader between both so I can update the Reader at home and work. I am thinking of adding a third (3rd) PC, my laptop, for altering content while I am traveling. I have never had a bit of a problem with the CONNECT software.
Having said this I now expect it to crash in 5 ... 4 ... 3 ... 2 .... 