I copied this from a file where I keep everything that might be useful some day. I have not read it or used it but it may solve your problem.
HOW TO GET RID OF THE LOGON PROMPT
del all *.pwl files in c:\Windows
del all entries under the [Password Lists] option of System.ini
reboot/restart the computer
You will get the LogOn prompt.
Enter your name. Do not hit ESC or close this dialog.
Hit the “ENTER” key or click OK.
Hit the “ENTER” key or click OK. (this is not a typo.)
reboot/restart the computer
Are you no longer plagued with the log on prompt?
If no, you’re done, if yes, keep reading.
|START|SETTINGS|CONTROL PANEL|PASSWORDS icon|USER PROFILES tab
|make sure that “All users of the PC use the same …” is selected
|OK button
|START|SETTINGS|CONTROL PANEL|NETWORK icon|CONFIGURATION tab
|PRIMARY NETWORK LOGON field|select “Windows logon”|OK button
(Between you,me and the fence-post, I’ve never found that step to be necessary.)
reboot/restart the computer
You will get the LogOn prompt.
Enter your name. Do not hit ESC or close this dialog.
Hit the “ENTER” key or click OK.
Hit the “ENTER” key or click OK. (this is not a typo.)
reboot/restart the computer
Are you no longer plagued with the log on prompt?
If no, you’re done, if yes, keep reading.
If you have TweakUI from the powertoys installed, then:
|START|SETTINGS|CONTROL PANEL|TWEAKUI icon|PARANOIA tab
|uncheck “Clear Last User at logon”
|NETWORK tab (in TweakUI)
|uncheck "Log on automatically at system startup
|APPLY button|OK button
Reboot, that is,
|START|SHUTDOWN|“Restart the computer?” item"|YES button
You will get the LogOn prompt.
Enter your name. Do not hit ESC or close this dialog.
Hit the “ENTER” key.
Hit the “ENTER” key. (this is not a typo.)
Reboot
More info on passwords : PC WORLD December 1999 page 310