sp_addserver

[NickKnife]

Hi guys
I was busy renaming my server and sp_dropserver worked but when it tried to execute sp_addserver it threw an error saying the server already exists. why did this happen and how do i fix it so that @@SERVERNAME is equal to the server name (at the moment it is null).
Thanks
Nick

[MAK]

--Sysservers table
Use master
go
sp_configure 'allow updates',1
go
reconfigure with override
go
update sysservers set srvname='newservername',
datasource='newseervername' where srvid=0
go
sp_configure 'allow updates',0
go
reconfigure with override
go

--Sysjobs table.
Use master
go
sp_configure 'allow updates',1
go
reconfigure with override
go
use msdb
go
update sysjobs set originating_server ="newservername"
go
sp_configure 'allow updates',0
go
reconfigure with override
go