Those who do not learn from their mistakes are doomed to repeat them. Yep.
About a year ago I did an upgrade for a company from SharePoint Services 2.0 to 3.0 and basically fought it for 3-weeks on and off. I just did an upgrade for the company I worked for again and sure enough the exact same things happened. I assume you are here because the SharePoint upgrade didn't go quite right for you either. Maybe you didn't have all the permissions needed, you had administrative rights to the server but not the database, oops. I am blown away that the installer will let you corrupt the database to an unusable state, no fear, you can recover and here is how.
What you see: Unable to get global configuration data
This is the first indicator of trouble, for me it meant that I had partially updated my database schema but rolled back my WSS to 2.0.
Do This: Rerun the upgrade to WSS 3.0 and follow through the upgrade handling any errors below.
What you see: An Microsoft.SharePoint.Administration.SPServer named "sql" is using the same id as the new object named "sql" of type Microsoft.SharePoint.Administration.SPServer. Every object must contain a unique id. Either update the new object's id or delete the existing object and try again.
Do this: Clear out the Dependencies and Objects tables. To do this, go to Query Analyzer or Microsoft SQL Management Studio (Express) and enter "delete from objects; delete from dependencies;", select the SP database and click on EXECUTE. If you try to do these individually, you will get dependency errors that are pretty miserable to resolve. I know, I did first.
What you see: The pre-upgrade scan tool has not yet been run on this database SPContentDatabase
Do this: From a command line run: C:Program FilesCommon FilesMicrosoft Sharedweb server extensions12BINprescan /all then try the upgrade again