Hi,
After analysis of the registry CCleaner informed me that:
Abnormal extension
.---Stillwater-Cottage2b HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\FileExts\.---Stillwater-Cottage2b
The entry can be removed but I wondered whether is not caused by a pest. On the Internet, there is nothing about this format. Maybe you know something about .---Stillwater-Cottage2b?