WP was redirecting to install.php, I installed again and replaced old files with new one but lost all data. Before reinstalling I backed up all the data in public html to a new folder, After installing again I replaced all the new data including wp content, config.php and all other folders from the previous install, Then i logged into the wp admin panel and I was able to see the old plugins and themes and I reactivated all the plugins and the old them BUT the theme data is lost, all the posts have disappeared and all the plugin data is gone as well. I have checked and config.php has the old sql data, I have checked phpmyadmin and all the old data is there, Is there anyway I can get all the posts back and all My themes and Plugin data back.
Always try to backup the database too.
In your case, probably the old database is replaced. See if you have a backup of database somewhere. Try to dig into wp_posts and wp_postmeta tables. Try to search old text from the old post and if you get results you are good, you can get them back, But if you don't have one then I am really sorry to say, Nobody can help you brother.