specified app/path cannot be accessed or invalid. when im trying to edit & install themes.what's the problem with me?

Your question will never get answered...
More info is needed!
What OS?
What version of litestep?
What theme are you trying to install, how are you trying to install it?

Immortal's right. You are giving us nothing to go on. from what you have said I would say you're doing it wrong but I don't know, lack of information on your part. You need to give us the details of what you have and what you are trying and how you are trying it. Without that you will no helpfull response from us.

ok, now i get it. i get the whole thingy now. but will it be possible in the future to skin the whole interface (not just the desktop) using this kind of approach?

If you want to skin all the windows use windows blindes. As far as what LS will be able to do in the future all depends on what we do now. If someone writes in that capability then yes, if not then no. As of right now the future lies within the hands of the dev team and some very dedicated people doing what they can to improve LS for all. It is up to us to do what we cant to help them or the community in any way we can.

jeffdied: read the *windows styles* thread.