Old sites showing up in replistor

Hi Everyone

I have updated our target replistor server to 6.4SP2 from 6.2. We have some sites that have closed and no longer need replicating and the actual servers have been shut down and the hardware decommissioned. However some of these sites are still showing up on the replistor target server and I cannot delete them. They are "greyed" out, but if I right click on the site, the delete option is greyed out as well, only attach, add and properties are available. Can anyone help?! Thanks.