Usually the problem arises after upgrading firebird 2.5 to 3.

Solution:

  1. Unistall firebird
  2. Delete folder C:\Program Files (x86)\Firebird\Firebird_3_0
  3. Delete fbclient.dll from folder  C:\Windows\SysWOW64
  4. Delete msvcp100.dll from folder C:\Windows\SysWOW64
  5. Delete msvcr100.dll from folder C:\Windows\SysWOW64
  6. Install Firebird version 3 again.

 

Information about firebird files:
https://firebirdsql.org/file/documentation/reference_manuals/user_manuals/html/qsg3-disk-locations.html