Problem with persistent administrator

Greetings

have recently reinstalled XP over a copy that turned out not to be OEM however the probme was probably there before.

When booting from scratch the system always logs into the Administrator login which appears to have a password (which I don know) but does not prompt for it.

This is with Welcome sceeen and fast user switching on.

if you do a logout from the admin user then gour get to see the other two user accounts on the systme and can access them correctly. But i haven't been able to disable this auto login.

Help

Graeme