Windows 7
GNU Emacs 27.0.50 (build 4, x86_64-w64-mingw32) of 2018-01-27

How to reproduce the bug:
1. create a Folder named "a.tar" or "a.zip" in local PC
2. load tramp
3. in dired, press Enter or dired-find-file on "a.tar" or "a.zip"
4. it reports: tramp-error: Package `tramp-archive' not supported



Best Regards,
Shuguang Sun