I added an entire drive as a custom VST folder and now Reason doesn't launch

If you added an entire drive (or a very large folder) as a VST folder on the Advanced tab in Reason's Preferences, resulting in that Reason/Suite/Intro/Lite doesn't launch (or stops responding), proceed as follows:

Quit Reason/Suite/Intro/Lite and then delete the following file:

Windows:

• The "Reason Plugin Dirs.prf" or "Reason Plugin Folders.prf" file in
  %APPDATA%\Propellerhead Software\Reason\ (if you are using Reason)
• The "Reason Suite Plugin Folders.prf" file in
  %APPDATA%\Propellerhead Software\Reason Suite\ (if you are using Reason Suite)
• The "Reason Intro Plugin Folders.prf" file in
  %APPDATA%\Propellerhead Software\Reason Intro\ (if you are using Reason Intro)
• The "Reason Lite Plugin Folders.prf" file in
  %APPDATA%\Propellerhead Software\Reason Lite\ (if you are using Reason Lite)

or

Mac:

Delete the "Reason Plugin Dirs.prf" or "Reason Plugin Folders.prf" file (if you are using Reason), the "Reason Suite Plugin Folders.prf" file (if you are using Reason Suite), the "Reason Intro Plugin Folders.prf" file (if you are using Reason Intro), or the "Reason Lite Plugin Folders.prf" file (if you are using Reason Lite)

in
~/Library/Preferences
The user (~) Library folder is hidden by default. To open it, press the Option key while opening the "Go" menu in Finder, then select "Library".

Then, launch Reason. Now, only the default VST Plugin Folders should be scanned.