Having Problems installing Micr. SQL Srvr 2k on Win XP OS

I get error mssg that say I need a valid sa password or I have not installed sql server 2000 on this system. can someone help me or point me in the right direction, please.
Singing- *Rain drops keep falling on my head*
Comments
If you already have MSDE or are installing on XP Proffesional, check if you're using both SQL Server and WIndows Authentication. BTW, it's god to use the dot "." in the server combo box as a habit. It limits the chances of you entering a wrong local host or ambiguous name.
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