>>How can I get the folder where FireBird is installed.
>>I use Delphi and I want to copy the UDF folder after a silent installation.

Not sure if this is the best method, but I read the DefaultInstance registry key. It work for me for FB 1.5, 2.1 and 2.5:

RootKey := HKEY_LOCAL_MACHINE;
Found := MyRegistry.OpenKeyReadOnly('\SOFTWARE\Firebird Project\Firebird Server\Instances');
if not Found then
Found := MyRegistry.OpenKeyReadOnly('\SOFTWARE\Wow6432Node\Firebird Project\Firebird Server\Instances');

If Found then
Result := MyRegistry.ReadString('DefaultInstance');


Regards
Maya


PS. Pardon the lack of object creation, etc, I have a few sub procs hat I merged this together from, so you get the gist