I took another look at the poll stuff:
w3t_Polls.P_Name (timestamp concatenated with username)
w3t_Polldata.P_Name (timestamp concatenated with username)
w3t_Polldata.P_IP (username or IP address)
I don't think converting the P_Name columns is important, since that appears just to be a way of uniquely identifying the poll. (And it would be messy to convert.)
But the P_IP column is evidently how the script keeps users from voting more than once, so that probably should be converted.