Here is a <a href=”http://www.phwinfo.com/forum/ms-sqlserver-setup/201362-sql-2005-database-default-location-during-setup.html”>good discussion </a>which may help you.
When you get to the list of services to install, click the Advanced button. Expand the SQL Server engine menu item, and select database files. Change the folder here. This will set the data file and log files to the same thing. You’ll need to change the folder to different folders after the install is finished.