SQL 2000 SP4 Upgradation Error - Error running script: sp3_serv_uni.sql (1)

First of all, I want to let you know that when you are upgrading SQL Server 2000 to SP4, make sure that you are Stopping and Changing startup type to Manual for below Services

1. MSSQL$Instance
2. Windows Management Instrumentation
3. Microsoft Search
4. SQLAgent$Instance

If you perform the above steps then you will never face issue while upgradation.

Incase you get below error "Error running script: sp3_serv_uni.sql (1)" then solution is to rename dbmslpcn.dll in C:\Windows\system32 and run setup so that dll will be created automatically.