As others have stated, to remove a Cache from the "Find Geocache" folder, you need to click "Log Attempt" than click on "Found" this will change the icon on the map and remove it from the "Find Geocache" list. It will place it in the "Show Found" List. The only way I know of to remove either Found or Unfound Caches is to connect to you computer: 1) when Autoplay screen comes up, click on "Open Folder to View Files" (if Autoplay does not come up, go to My Computer double click on the "Garmin" icon) 2) Open "Garmin" Folder, 3) Open "GPX" Folder, 4) all of your cache files will be listed there by GC Code. You can delete any or all. You can also organize your caches.
You can store a lot of found caches on your GPS
Waypoints can be removed with "Waypoint Manager"
Now if I only knew how to view comments entered about a cache. You would think that for the price they get for their GPS, Garmin would have a decent owners manual.