What are the difference between load/unload, uninstall/install?
'Install' a font will install it to system and write it to registry.
'Load' a font will install it to system without writing registry so they are present in current session only.

When you select several fonts, then click
• 'Uninstall' command, it will remove installed fonts from system as well as registry, if some loaded fonts included in the selection list, they will be unloaded.
• 'Unload' command, it will remove loaded fonts from system, if some installed fonts included in the selection list, they will be uninstalled while physical files won't be moved.

What are 'Bookmarks'? What do they do? How do they work?
Bookmarks are simply links which provide quick and easy access to your favorite font folders. With "Bookmark" you can jump directly to where you want.

To bookmark a folder, do either of the following:
• Select the folder in 'Browse' tab/bar, click application menu 'Browse'-'Add to Bookmarks', or through command either from toolbar dropdown menu or right-click mouse context menu.
• Click application menu 'Browse'-'Edit Bookmarks', a dialog will display to help you add and remove folder bookmarks.

Note: The folders bookmarked are different from those appear in the histroy list. The history list only saves 10 most recently visited folders, while bookmarked folders would never been swapped out by newly visited folders.

0x80040154: Class not registerd
The error seems that MSXML shipped with FFR setup package was not installed properly, which is essential to operate on FFR's font sets. Perhaps you could download and install MSXML component seperately. After it were installed, you could run FFR to handle your font sets.
Please get the MSXML here. From the web page, please click "Download" button on the right of file named "msxml6_x86.msi". For 64bit system, please select "msxml6_x64.msi".
Once download completes, please double click it to install.

What are font sets 'databases'? What do they do? How do they work?
A font set database is a file storage to hold font sets details such as set names, default font folder for each set, every font name as well as its file path, etc.
Working database is displayed under the 'Font Sets' tab/bar. Set management functions can be performed on each set or font within a set.
When the application is installed and start to run, a default database is created automatically, you might use it for all of your work sets. However, you can create as many database for any purpose as you like.
Note that only file path is saved in database, not the physical file.

By default, the font fitting room installation has a default set named "Starter Set" which pointed to Windows fonts folder. Can I removed this set?
Sure, no problem.
This set is just a set of bookmarks of system fonts in case of system corruption, you know the minimum set of fonts that system needs.

i got a new computer and want to use my fontfitting room on that computer now... but can't find out how to do it?Can you help me?
To recover FFR Deluxe, please backup a few files as following,

• The database file.
  To find out current font sets database file, click menu command "Sets"->"Current Database", on the dialog, you could see the database file path and name. Clicking "Windows Explorer" button to open Explorer where you can copy the database file.
• Aplication settting file.(optional)
  That's the application configuration file which saves folder bookmarks, preferred preview strings and styles, window positions from last session, etc.
  You can find this file named 'ffr.ini' in the CSIDL_LOCAL_APPDATA (Local Settings\Application Data) path.
• Fonts in each set.(optional)
  The physical font files.
  Font sets database only records the font file path, so if the physical file is not in the path recorded, the font won't be able to be activated/deactivated.
  If this is the case, don't worry, there are commands to correct the font paths.
  • To correct set's default path, select it, then click "Sets"->"Change Default Path..."
  • To correct a font path that is not same as set's default path , select it, then click "Sets"->"Repair Font Path..."

Then Copy the database file to anywhere on your new PC. In FFR, click "Sets"->"Open Database...", select the copied database file.
Now font sets are appeared on your new PC. You can further correct the set's default directory to make it point to the physical font folder if not in the same path as old machine.