If one of the other helpful links does not solve the problem it might be due to there being a hidden file in the directory (why I have no idea).
But you might want to be sure you can see hidden files just in case.
Windows Explorer (the little Windows Flag and E key on your keyboard)
Highlight the directory d:\thorui\ and click on tools then folder options and file type then go down the long list and make sure you have "Show Hidden FIles"
