Why do I always get "cannot write please remove the write protection" when I copy files on C: ? I selected that my account have full control, but i still get this error. What can I do ?
Even though you have full control, if a folder is "read-only" it will prevent you from copying files into it. Full control allows you to change the properties to read/write, and then copy the files.
If you could copy files into read-only folders, this would have some unhelpful consequences.
However, it would be odd if the root of C is read-only. What folder are you trying to copy into?