I clicked a link in a video education site which was said to download Quicktime. The download failed and I am left with an icon which says 'quicktimeinstallerx.dmg. When I click on it I get 'failed to mount due to error 95(no mountable file systems). When I try to drag it into the trash I get a box 'The item quicktimeinstallerx.dmg is being used by another task right now. (Other tasks include, moving, copying or emptying the Trash.) Try again when the other task is complete' These is a barberpole scrolling sideways. How do I get this thing off my desktop?