SharePoint Configuration && SQL Express - Error 4060

While trying to "Set Configuration Database Server" for Windows SharePoint Services I receive the error:
"Cannot open database "SharePoint" requested by the login.
The login failed. (Error code: 4060)"

I set up a test bed server 'SNET' with WinServer03 SP1, IIS 6. SQL Server Express, and SharePoint Services.

In "Set Configuration Database Server" I used:
Database server: snetsqlexpress
SQL Server database name: SharePoint (I know real imaginative)
Database connection type: * Use Windows authentication
X Connect to existing configuration database.

If I try "Use SQL Authentication"
"Login failed for user <username>. The user is not associated with a trusted SQL Server connection. (Error code: 18452)"

First let me say that while I'm not a newbie, as usual I've bitten off more than I can chew comfortably. Server '03, Active Directory, IIS 6, SQLExpress, and SharePoint are all relatively new to me, hence the test bed server, and I'm on a pretty steep learning curve.

But what's life without a challenge.

So the short and sweet of it is can somebody point me in the right direction to find the root cause of this error. I do have other programs running with this instance of SQLExpress and doing so quite happily. And I've given myself god privileges in AD just to try to get around this.