There is no supported way of doing a 'manual' installation of just the database.
An easier way would be to use a test server with the same SQL version as the production database server for the ePO install. Once the installation is done, stop the ePO services, take a backup of the ePO database and restore on the production.
Alternatively you can consider detach and attach to the production server.
The third and 'unsupported' option would be to script the entire database and its contents from the test sql server and recreate the database on the production - there are third party sql database tools which accomplish this.
Hope that helps.
Try create a new database in SQL Server 2005, with sugested name ePO4, and proceed with install. When install ask for the database, select ePO4.
You can't install to a previously created DB. The install script uses a CREATE DATABASE which can't be bypassed. The only way to create the ePO DB is via the installer.