Sometimes you will run into errors on Windows that prevent you from deleting files or folders. The error message will look something like this.

There are 2 ways to fix this issue. First one is to use this force delete batcher. Just change the path to the directory and then click it. You should see the file disappear. 

Another quick way is to use Winrar. Right click the folder and in the context menu youll see Add to archive. Click this and it will bring up a dialog. Be sure to tick Delete files after archiving. This will zip the folder and remove it from the directory. Now you will be able to delete the .rar.