it's rather curious that it is redirecting to the admin_cms/users_login.php folder,the PowerCMS Package does not contain an admin CMS folder. it contains an admin folder.
Did you rename the admin folder to admin_cms?
where there any other folders that you renamed?
You should not be renaming any of the folders or files, this will break the links.
It doesn't look like all of the files where uploaded to your site.
if you uploaded the power cms files to:
there should be an install folder at:
gives me a 404 page not found error.