Sounds like a permission error. Try it as Admin. Or try this:
- In Windows Explorer, right click the folder you want to be able to delete from.
- Choose Sharing and Security.
- Click on the Security tab.
- If your Media Center user is not in the list, click Add and use the dialog box to add the user.
- Click Advanced near the bottom.
- Select your Media Center user and click Edit.
- Make sure that Apply Onto has “This folder, subfolders and files” selected.
- Check “Delete Subfolders and Files” and “Delete” in the Allow column.
- Click OK, OK, OK.