WI Configuration to use - Delete

That's pretty much all you can do.  But BE VERY CAREFUL as it will be major PIA to restore a Configuration deleted by mistake.

I would suggest you export all of your configurations before undertaking your cleanup.

Just to add to JohnnyQuest  answer,

1) Ensure that the website configuration template is not being used on any of your web servers (if you have more than one)

2) If you have been through multiple upgrades, you might be able to more easily target the sites you want to remove, as the description value of the Web Interface (within the node you mention) usually has a number at the end, the highest number SHOULD be for the current version (lower numbers are migrated templates from a previous version).

3) For the sake of a couple of minutes, also do a DB backup (more a belts and braces approach)

Well said Stu.Pollock .

Note:

Braces = Suspenders for those outside the Commonwealth.  

Thanks both. I took a backup just in case and have now cleaned out all the rubbish. I have a nice clean configuration. 

Thanks both. I took a backup just in case and have now cleaned out all the rubbish. I have a nice clean configuration.