How to delete files and folders that cannot be deleted?

del is for deleting files, rd aka rmdir is for deleting folders, so...

rd /s "\\?\C:\1\2\Favorites\Wien\What To Do.."

...should do the job! :-)

The /s parameter

removes all directories and files in the specified directory in addition to the directory itself.
Used to remove a directory tree.

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If this doesn't work; even not with wildcards/auto-completion; then you have corruption issues.

You very likely have FS(filesystem) corruption. Run a chkdsk then attempt to remove the files.

Also make sure nothing is in use within the directory as the warning suggests.

I would also recommend making a backup of your important files before anything.

I would try running chkdsk first as Jeff suggested. If this does not work, you could boot up with a linux live cd, mount the hard drive and delete the folders from within the linux live environment.