When you upgrade from Win98 or WinME:
Dial-up connection passwords 
Logon passwords 
Domain passwords 
Network share passwords
are NOT persevered.

NOTE: This doesn't happen when you upgrade from Windows 2000.

The listed Windows operating systems do NOT store passwords in a secure manner. You must re-create the passwords when prompted.

NOTE: If you uninstall Windows XP, the passwords are NOT recovered.