There's some confusion here that I'd like to help with:
- The files in question (animation gifs and sounds) are stored in the device ROM. They are not in Storage Memory.
- Because of #1, it does not save any space to "overwrite" any of these files with a different one, with the same name. When you do that, what happens is the new file consumes some real Storage Memory, just as if you'd given it a different name, and the filesystem updates internal FS pointers to point to the file in SM.
- This is why (#1) when you try and delete any of these files, reboot, and looks in \Windows they are still there. They can't be deleted -- they're in ROM.
- Again because of #1, it is why some people can't find them; depending on the File Browser you are using, you have to tell it in settings to show files in ROM. I use Resco Explorer, and I have to do exactly this to see these files. I have to do this to see other files, like PowerCalc.exe. In fact, turning on ROM files loads \Windows with a bazillion files and makes it cumbersome to browse, so I leave this option off unless I have a specific need to see these files. I don't know if it is even possible to view the ROM files in the stock WM6 File Browser.