When you install the Firebird database system it is recommended you use the default directories and other options. The main decision is to select the right components.
The default settings shown above will work fine. Most users will not have a need for the "Developer and admin tools components", so un-ticking that item is a good choice as they use quite a bit of disk space.
The second set of options appear as:
It is recommended you leave these as they appear by default and as shown here. Only people wishing to use Firebird for applications other than the ASE Scorer Version 9 should consider changing these.