.DS-Store is supposed to be invisible & is in all osx folders. It contains os information on folder settings. If you remove the . from in front of the file/folder it will become visible. There are utilities around that can make all files & folders visible(/invisible), but normally such invisible files should remain so.
Problem trashing certain files or folders because they're locked? 2 ways in OSX. One is to get info for that item & uncheck the locked option. Another is to empty trash whilst holding down the Option key. A 3rd option is to put the item into a folder & put another item into that folder of the same name so you're replacing it but that doesn't always work. A 4rth option is to start up in another OS, be it OS 9 or another OSX or a startup disk.