When i connect My WD External Hard disk it restarts the pc

I bought WD My passport 320gb 2 weeks a go. It was working properly but i connect it to a Toshiba laptop which has a trojan virus, now when i try to connect My Passport WD External Drive To another PC it keeps Restarting the pc and if i connect it to a live pc it will automatically shut down the pc.  

All my Files are in this hard disk please i really need help. 

windows restarts or your laptop just stops - like the power / battery was removed?

so when you plug it in and turn on a pc, it just keeps restarting during reboot?