When Preview pane is enabled word documents give error: Word could not create the work file. Check the temp environment variable (microsoft.com) 


Please make sure you back these keys before you delete them


browse to HKEY_LOCAL_MACHINE\SOFTWARE\Classes\CLSID\

Backup the CLSID

Delete keys:

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\CLSID\{00020827-0000-0000-C000-000000000046}

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\CLSID\{65235197-874B-4A07-BDC5-E65EA825B718}

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\CLSID\{84F66100-FF7C-4fb4-B0C0-02CD7FB668FE}

Reboot.
Test.