Thank you pilot9 for your response. It's now too late for me, I already reinstalled linux on that server.
However, I'd like to know more details about this issue and how to avoid it in the future. I don't understand your case. Are you nice to explain a bit more detailed? If you can, please clear up the prefixes staff, as I don't understand why and when is it write to use them. I assume you installed drupal, and after that the hell began. Am I write?