From the docs that came with firebird :
Important notice for 64-bit Windows users
On 64-bit Windows systems, the “Program Files” directory is reserved for 64-bit programs. If you try to install a 32-bit application into that folder, it will be auto-redirected to a directory which – in English versions – is called “Program Files (x86)”. In other language versions the name may be different.
In the same vein, the System32 directory is reserved for 64-bit libraries. 32-bit libraries go into SysWOW64.
That's right: 64-bit libraries are in System32, 32-bit libraries in SysWOW64.
If you're not aware of this, you may have a hard time locating your 32-bit Firebird components on a 64-bit Windows system.
(Incidentally, WOW stands for Windows on Windows. Now you can also work out what LOL means.)