I installed apache solr on drupal 5, now when I perform a search using Admin I get results but I do not get any from Drupal.
I'd double check that Drupal has permission to create temporary tables within the database. If not, you'll always get 'no results found' when searching.
You probably have a permissions issue. Since you can access search results from admin, the search engine and -indexing is working. Drupal admin search returns all entries, regardless of their status (published, unpublished, draft) or their access (many flavours of content-access modules exist).
First, verify that the nodes are actually visible on your site as "normal" user: anonymous or loggin in. If so, there is not an access-problem and nodes are published. Secondly, verify that you have no access-module, such as organic groups or domain running: that may be configured slightly wrong, or used in a strange way, and disable access to content under certain conditions. Thirdly, verify that you are not running any search-related modules. Maybe you installed a module that "enhances" or "overrides" search? Such a module would not change the behaviour of admin-search, but would change what is seen at the search results.
If none of these apply, then please post more infomation.