If I right click RTF or DOCX in Book Details and select
Open xxx With I get following error :
Spoiler:
calibre, version 2.21.0
ERROR: Unhandled exception: <b>error</b>

2, 'ExtractIconEx', 'The system cannot find the file specified.')
calibre 2.21 [64bit] isfrozen: True is64bit: True
Windows-7-6.1.7601-SP1 Windows ('64bit', 'WindowsPE')
('Windows', '7', '6.1.7601')
Python 2.7.9
Windows: ('7', '6.1.7601', 'SP1', 'Multiprocessor Free')
Successfully initialized third party plugins: Import List && Goodreads && Resize Cover && Quality Check && EpubSplit && FictionDB && Count Pages && Walk Search History && Beam Ebooks && Barnes & Noble && Reading List && Quick Preferences && Find Duplicates && Extract ISBN && View Manager && Open With && Generate Cover && Modify ePub && Favourites Menu
Traceback (most recent call last):
File "site-packages\calibre\gui2\open_with.py", line 267, in programs_found
File "site-packages\calibre\gui2\open_with.py", line 82, in entry_to_item
File "site-packages\calibre\utils\open_with\windows.py", line 110, in load_icon_resource
File "site-packages\calibre\utils\open_with\windows.py", line 36, in simple_load_icon
error: (2, 'ExtractIconEx', 'The system cannot find the file specified.')
The Windows Shell Open verb is to Office 12\WINWORD.EXE if that's relevant. .ONE and XLS files are fine, not tried PPT ('cause I don't have any)
Hmmm - I also get the same error on video and audio formats, momentarily I assumed it was a Winword only speciality
No hurry for me on this.
PS - I do like this feature, it means I can have direct kb shorts rather that going via the View menu.
BR