1. SQL Server 2008 is back compatible with SQL2005. So, if you still want to use 2005 version, you create 2008 and change compatibility to 2005. It will turn off all new 2008 features.

2. To manage you SQL Server 2008 and older SQL Server 2005, you can upgrade your SQL Studio Management to v2008 by going to this link:
http://www.microsoft.com/express/sql/download/default.aspx

Source and Discussions:
https://community.aspnix.com/t/3157.aspx