Unable to connect to any database

I have just downloaded your free trial, installed it, and attempted to connect to a database.
It failed always: Oracle Library ODC.DLL could not be loaded.
Thanks for your help. Samir

Do you have 32-bit Oracle client installed? Is it in the system search path?

Yes of course, Oracle Client is installed and works for all other apps that I use.
Even your software found tnsnames.ora and copied to folder "reports" !
Still login screen under "database" the list is empty.

DB Audit does not copy tnsnames.ora nor it creates any "report"s folders. Indeed it can read names from tnsnames.ora file if it can positively identify the default oracle home.

The error message says "Oracle Library ODC.DLL could not be loaded. " this is typically reported when Oracle client isn't installed. But in your case you say it's installed.
Let's check 2 things
1. If you have multiple Oracle homes and/or multiple Oracle clients - need to verify the default home is specified in the registry or environment variables so that DB Audit can locate it. You can use Oracle Home Selector to set the default home.
Please see http://docs.oracle.com/cd/B10501_01/em.920/a96697/moh.htm depending on your system type either "Home Selector (Available on Win32 Platforms)" section or "Oracle Home Directory Structure for Windows Platform"
2. If you don't have multiple Oracle homes, please verify Oracle's OCI.DLL is located in the system search path, in other words if the Oracle's client BIN directory is listed in the system PATH environment variable.
3. Very important: Make sure the Oracle client path references in the PATH environment variable points to 32-bit version not 64-bit version.

Just in case, the web-based DB Audit Management Console doesn't need Oracle client or other middle-ware to connect to Oracle servers, it connects directly to the server. If you haven't already installed it, you can install it using the same installation program you used to install the graphical version of the Management Console.