SQL Server 2000 : Upgrade from Personal Edition to Enterprise Edition I've never tried this before but this is what I'm attempting to do : 


Backup all the databases
Copy current master.mdf and master.ldf to another location (for later purpose) 
Uninstall SQL Server 2000 Personal Edition
Install SQL Server 2000 Enterprise Edition (SP4)
Stop the newly installed server, and replace the master.mdf and master.ldf with those old two files above 
Restart server 


I've done this before, but only with Enterprise Edition, after reinstalling SQL Server I'll just have to replace the master file and everything is fine. 

Will it work in this case ?
I would like to post this as answer what is point in upgrading to SQL server 2000 which is outdated completely without any support. Even it is not good for testing purpose. Its like using typewriter in era or super computers.

Dont uninstall personal edition first. Install enterprise move databses by backup restore method. If you restore master msdb databases you would not need to move logins and jobs.

Please refer to below link

https://www.barracudaware.com/files/docs/9.00/help/restoring_microsoft_sql_server_2000_master_database.html