Can't unlock a file

Okay, so, I found a lot a stuff on how to unlock a file, and I know how to, using the get info window, but one of my apps, when I "get info", the checkbox is grayed out, and I cannot uncheck it. I've tried dragging it to the trash, and it won't do that either. I get a window that says that "file locked and cannot complete operation." I've tried the little "locked" app, and it didn't do anything. Permissions are read and write, and I'm the only user on the computer. Any ideas?

If this is already discussed, could I be directed to where? I looked for a good hour, here and on other forums, but couldn't find anything.

I tried the terminal thing, but it asked for a password. I tried typing my system one, but nothing showed. I was hitting the keys, but no text came up.

So, even though I'm not seeing anything when I type system password, it's really there?

It worked! Thanks a lot! I can't believe that did it, but it did. Again, thanks for the tip!