Hmm, that page appears to no longer exist. I'll attach the installer to this post.

Even if you closed all the programs in Task Manager, there are still processes running that can be using the file. For example, I've noticed that several P2P programs don't appear in the Applications tab of the Task Manager when minimized to the system tray. Many times when you want to move a file that has just been downloaded from that program, you get the message that the file is in use, because the program is using it.

In every case, the program using the file must be shut down before anything can be done with it (aside from opening a new instance of it, which can be done with most files, like playing a video in WMP while it's being uploaded to someone on Kazaa).

If you use the program I've attached and it says explorer.exe is using the file, it might be a case of the window the file is selected in is displaying the video on that preview pane of the web interface. Sometimes closing the folder will solve the problem, sometimes opening the folder and selecting another file (forcing a new preview) will do it.

Good luck!