Connecting using passwordfile only?

I am using a password file to authenticate users, weird thing is that when logging in to server (locally) this morning I was able to connect using internal without a password.

Yet.....
# SQLNET.AUTHENTICATION_SERVICES= (NTS) is commented out!
remote_login_passwordfile = exclusive is set!
ORA_SID_PWFILE registry key does not exist!
ORA_DBA group does exist in WinXP and am logging is as XP admin but because of above I should still need a password for logging in as internal in oracle, right?

Relogged into XP as admin after checking a guest account access (no access without internal password :) there), now find that if i try to login as internal I need the password, can anybody offer any suggestions as to why one minute i can log in using internal with no password and the next minute I can't?

Cheers
Gus