Hi Jake,
Thank you, I was able to delete the feature datasets. They do not appear any more when i log-in using ArcCatalog.
When I was checking the SDE.GDB.ITEMS, I Notice that the records for the features classes that were inside the feature datasets. When I try to delete them i get the following error.
A problem occurred attempting to delete row 3.
Error Source: Microsoft.SqlServer.managemnet.Data
........ "sde.sys.geometry" is invalid
(See attach graph)