even there is no user/pw then just hit enter/go and see if it goes past the unlock screen.
if that doesn't work then contact the person you bought it from and get the username/pw to unlock it.
if that doesn't work, take out the battery put it back in, hold down the home button and power button until you see a triangle with an exclamation mark then press the search button (the magnifying glass)
then using the volume keys on the side, scroll to wipe cache partition, select with the red camera key on the side of the phone, select yes, then go back to the menu with the back key, scroll to and select the wipe data/factory reset the same way you did the cache
then go back again to the menu, select the apply update.zip, select yes,
once this says done, you may have to manually reboot by going back then selecting reboot system now.
this will restore the phone to the factory settings like it is brand new out of the box. sounds difficult but it is really easy, and don't worry, if you can't unlock the phone anyway, then you really can't screw it up any more than it already is.
if you aren't sure about anything listed above please feel free to ask as many clarifying questions as you need to, we are all here to help.
welcome to android!
