SplendidCRM is a simple product and can be uninstalled manually.  The first thing you will want to do is manually uninstall the database.  In the Control Panel, look for and uninstall Microsoft SQL Server Desktop Engine (SPLENDIDCRM).  Once the database has been uninstalled, I would probably try and using the install utility again, but I would only wait 5 minutes before aborting.

The next step is to remove the virtual directory from Internet Information Services (IIS).  You can find IIS in the Control Panel under Administrative Tools.  You first expand the tree on the left until you see SplendidCRM.  You will find it under (local computer \ Web Sites \ Default Web Site.  Then right click on SplendidCRM and select Delete.

Now you can delete all the files in "C:\Program Files\SplendidCRM Software". 

The last step is to remove the registry entry, but this is dangerous unless you know what you doing.  If you have never edited a registry entry, then I don't suggest that you start now.  However, if you do know what you are doing, you can find the Installer entry somewhere under HKEY_CURRENT_USER\Software\Microsoft\Installer\Products\.  Look for the SplendidCRM Open-Source product name.