-- For 2005, here is a simple script:

use msdb;

go

updatedbo.sysdtspackages90

setownersid = (

select sid from msdb.sys.syslogins where name = 'LoginNameHere')

where [name] = 'MaintenancePlanNameHere';

--------------------------------------

-- and for 2000,

use msdb;

go

update sysdbmaintplans

set owner = 'LoginNameHere'

where...