New Post: write permission httpdocs folder

Hi,

I have deployed my site to server, when I install add-on such as: AddThis, Facebook Like Button,...
It cause error: "The Windows user under which this C1 instance is running does not have write permission to file or folder 'D:\hosting*****\httpdocs\'."
But on my Plesk Panel I cannot set permission for root folder.
Could you tell me some suggestions to solve this problem?

Thank you,