Hi HomerJ,
The good news is thag yes you can revert to the original qcsiteadmin_db and since you haven't activated your projects yet, the data will not have changed nor will you lose any work that may have been done since the changes (as none was completed).

What you will need to do is to stop the services and then edit the siteadmin.xml files to point to the original qcsiteadmin_db within that xml. As an example do the following within ALM 11 (the folder locations will differ with different ALM versions and different OS versions, so you may need to search for all instances and replace the information for each location to ensure it works as desired):

Start by changing where the APP server is to look for it's qcsiteadmin database.
Open qcbin20.war folder (folder name has a ''.'' In it):
3 locations - change all three (if they all exist)
C:Program FilesHPHP Application Lifecycle Management Platformapplication20qcbin.warWEB-INF
C:Documents and SettingsAll UsersApplication DataHPALMjbossserverdefaultdeploy20qcbin.warWEB-INF
C:Documents and SettingsAll UsersApplication DataHPALMapplication20qcbin.warWEB-INF
Navigate to the WEB-INF folder

Edit the project name from the new qcsiteadmin project db to the original one).

Once this is done, you can just restart the services and all should start normally and run off of the original db information.

You shouldn't but may have to remove (remove and not delete) the projects from the project list and readd them to the list if they are not able to be reactivated.

Hope this helps,
Dan