Upgrading from SQL Server 2005 to 2008

I have upgraded from SQL Server 2008 to SQL Server 2005 using the upgrade wizard. Once completed I found that SQL 2005 still exists. I used the same instance that was in SQL Server 2005, but I can’t connect. And all data, which are stored on SQL Server 2005, are not found on SQL Server 2008 with the same instance. Do I need to import the data manually? Or did I miss any steps during the upgrading?

From stackoverflow

• You may have not have performed an in-place upgrade correctly?
  Does the server now have two instances of SQL Server running? have a look in services.

  You can use the Database Copy Wizard to migrate your 2005 db's if you now have a 2005 and 2008 SQL running.

  You may also try attaching the 2005 mdf files from Management Studio in 2008, right click on user databases and select attach. This should allow you to attach the 2005 db's and upgrade them to 2008.