Installer deletes files

If you use the installer 'FirebirdSetup.exe', be warned that there is a possibility of losing some data if you're not careful.

If you select default installation - there is no problem. Firebird installs in C:\Program Files\Mozilla Firebird\

If you select custom installation, and mark the checkbox 'clean install', firebird setup will delete all files in the install directory. So if you mistakenly select C:\Program Files\ instead of C:\Program Files\Firebird, all your programs in C:\Program Files\ will get deleted.