My Passport causes serious system failures

last december i purchaised a WD 500GB passport intending to save data so that i could format my home PC, this worked fine but after the format i was having alot of system instability.

Now the only thing i cant rule out is the passport, the crash always happens withing 12 hours of connecting it ragardless of it being days or weeks after a fresh format, and  it is made worse if i leave the passport connected when restarting.

after the initial incident the system will run much slower and will often crash, and im wondering if anyone can tell me if Passports change system settings or install software when they are used.

What OS are you using and are you up to date on all drivers for your OS?