Error 53

I am having some issues deleting a few projects. I have admin rights but their are a few select folders which say Error:53 Projects not deleted.

I can Add/Delete other projects but not this group of folders for some reason. I can transfer the "tree" of projects to other locations. I can even add Subprojects but for some reason I cannot delete these 4 or 5 projects. Has anyone experiences this before?

SolidworksWorkgroup Pdm