How to delete an opening file

I failed to delete some files in the Vista system, below is the error message:



I don't think this file is in using because I reinstalled the related application to another directory, so I restarted the OS into safe mode, try again, I got the same error. so this file is not in using, it is a wrong indicator.

Perhaps it's permission which prevent me to delete the file, so I check the file permission:



Yes, even the administrator has no permission to delete this file. so we must assign sufficient permission to the current user (an administrator) :



The check boxes are grayed out, aha, it looks like the current user does not have the ownership.
Don't worry, as an administrator, you can seize the ownership from any user:



That's right! the current file owner is SYSTEM account, take it over:



Then reopen the file properities page, assign full control permission to the current user, delete the file, succeeded.

Vista is hateful, it mislead us by a wrong error message.