Many issues with an installation of Mathematica can be fixed by resetting Mathematica‘s preferences. Starting Mathematica with cleared preferences returns it to its default configuration by deleting and recreating internal files located in the Base Directory and the User Base Directory. You can find their locations on your computer by evaluating $BaseDirectory and $UserBaseDirectory in Mathematica.
If you have saved anything to these directories, please back them up before performing a clean start. If you have edited any init.m files, they would be located in these directories.
After performing the clean start, Mathematica may need to activate again. You can access your activation information for Mathematica through the Wolfram User Portal.


Windows

To perform a clean start on Windows, start Mathematica while holding down the Ctrl and Shift keys. Keep the keys held down until one of Mathematica‘s screens appears. If this does not seem to work, you can perform a clean start manually by deleting the Base Directory and User Base Directory on the computer.

On Windows 7, 8,  and Vista, these directories are located at:

  • C:\ProgramData\Mathematica
  • C:\Users\<user>\AppData\Roaming\Mathematica

where <user> is your username on the computer.

On Windows XP, these directories are located at:

  • C:\Documents and Settings\All Users\Application Data\Mathematica
  • C:\Documents and Settings\<user>\Application Data\Mathematica

where <user> is your username on the computer.

These files may be hidden on your computer. You may need to enable your account to see hidden files.

Mac

To perform a clean start on a Mac, start Mathematica while holding down the Option and Shift keys. Keep the keys held down until one of Mathematica‘s screens appears. If this does not seem to work, you can perform a clean start manually by deleting the Base Directory and User Base Directory on the computer. These are located at:

  • /Library/Mathematica
  • ~/Library/Mathematica


Linux

To perform a clean start on Linux, start Mathematica by running the following in your terminal:

mathematica -cleanstart

If this does not seem to work, you can perform a clean start manually by deleting the Base Directory and User Base Directory on the computer. These are located at:

  • /usr/share/Mathematica
  • ~/.Mathematica