Some help with themes

[ford-prefect]

Hi, I recently installed 8.10, and I'm having some trouble using themes. What I've tried to do is install a .tar.gz from gnome-look.org, but usually one of three things happen when I try to install it via Appearance Preferences > Theme, no matter the theme: 1) An error message comes up saying, "There was an error installing the selected file: 'The theme name' does not appear to be a valid theme." 2) An error message comes up saying, "Installation for theme 'Theme Name' Failed: Can't move directory over directory," or 3) it technically gets installed, but some error message comes up saying that it doesn't appear as it should because some theme isn't installed, but it doesn't specify which, it just shows up as ", one quotation mark, despite the fact that I'm almost positive I have the necessary themes installed beforehand. (These are usually mist and pixmap - they both come preinstalled, correct?) Am I installing them incorrectly? Is there something I need to install that I haven't? Thanks a lot for anyone who can help me.

[chriskin]

1)the first one seems to mean just that, what you are trying to install is either a wrongly made theme, or not a theme at all
2)the second seems to mean that you already have the theme installed, either as part of another or just by itself (for example dust extras has dust in it as well, so if you try to install dust after the dust extras one, you get a message of failure, or even the other way round, for a part of the extras)
3)might it say that the theme engine is not installed?