I can guarantee you that someone who isnt even capable of putting his/her/its question in the actual text box is going understand absolutely zero of what you just said. I dont even try to help these people any more. It's not like you're going to get a response or anything. On the other hand, it's a good source of free posts to go towards your forum rank.
Therefore I think it is for us to help them to start getting familiar with using the computer and bring their knowledge up.
Try restart your computer and delete it after restart. Also, if you really have no idea what livebriand is talking about, you can try using Unlocker to unlock the file first before deleting it. It works most of the time. Right clock on the file and select unlock then delete it as you usually would. The download link is below:http://www.filehippo.com/download_unlocker/
Even I know the kill task and unmount disk livebriand talked about I still use this software because it is much faster.