My best and safest bet would be to backup 2000 database and restore it on 2005 and change the compatibility mode, transfer logins using script given in this link, map users and logins, remove all the user schema's from database. If you have dts packages on 2000 server then save them into structured file and then move to 2005. (check legacy in M M Studio)

http://support.microsoft.com/kb/246133 -- Check method 2 for transferring logins from 2000 - 2005.