I had SharePoint 2010 Beta2 installed on a single virtual machine and decided to remove to to install SharePoint 2010 RTM version. So, I followed the following steps to remove SharePoint Beta 2:
1. Ran the configuration wizard and disconnected from the farm.
2. Uninstalled SharePoint from Control Panel
3. Uninstalled the SharePoint 2010 Beta prerequisites software.
4. Rebooted the machine.
After removing/uninstalling SharePoint 2010 Beta2, I went ahead and installed SharePoint 2010 RTM and after the SharePoint Configuration Wizard Completed successfully, I launched Central Administration site and to my surprise the icons looked strange, it looked like a combination of Beta and RTM.
Here is a screen shot of the ribbon after SharePoint 2010 RTM installation:
Here is a screen shot of the ribbon from a machine that DID NOT have SharePoint Beta previously installed:
So, I disconnected from the farm and looked at IIS and found the following:
There is SITE_2. However, if you click on it from the left pane you get the following error:
I cannot say for sure that SITE_2 was the culprit, but I have learned my lesson by checking IIS to see if there are any leftover from previous SharePoint installation.