Migrating to SQL Server 2005 on same machine

I'm planning a migration from SQL Server 2000 to SQL Server 2005. To do thi
s
migration I have the contraint that I can't buy new machines. So I'm trying
to determine what options I have. First let me set the stage a little. For
a given SQL Server production machine I may have from 10-50
databases/application running. So I'm looking at the following options. Ar
e
there others? What are the risks of each of these. If you were me which wa
y
would you go, consider the constraint above.
Option 1: Upgrade In Place - This option would upgrade all database to from
SQL Server 2000 to SQL server 2005 at the same time by SQL Server machine.
Option 2: Run a named instance of SQL Server 2005 - This option would
install a named instance of SQL Server 2005 on the same machine that is
running the default instance of SQL Server 2000. Databases would be migrate
d
one at a time, or a handful at a time, until all database have been migrated
.
Once all databases have been migrated, SQL Server 2000 would be shutdown.
What are your opinions of how successful would each of these options be?
What are this risks of each option? Does running two instanances of
different versions of SQL Server cause any issue?If you have only one machine , I would recommend install SQL as a named
instance, and when you migrate all of the databases and test them
thouroughly you can stop SQL Server 2000.
Regards
Amish Shah