Copy here content of firebird embedded 32b client (ex: Firebird-2.5.7.27050-0_Win32_embed.zip).
Same with firebird_bin64 with 64b version (ex: Firebird-2.5.7.27050-0_x64_embed.zip).
Replace existing files with new ones except conf file.
Rename fbembed.dll fbclient.dll. This is required to run gfix.exe.