Unable to delete .avi files. Try the below steps.

You might have downloaded .avi files from net and this might be a tracker or something that will always be occupying space in ur hdd. When u try deleting it, following message get popped up "unable to delete, file is being used by another program or person". Even if you try to close all the process in task manager except explorer in task manager, u still won't be able to delete the file.

I really don't know the reason why this file can't be deleted. But I know a workaround to delete this file.

1. Open a Command Prompt window and leave it open. Close all open programs.
2. Go to Start > Run and enter TASKMGR.exe. Go to the Processes tab and End Process on Explorer.exe. Leave Task Manager open.
3. Go back to the Command Prompt window and change to the directory where the files are located.
   
4. At the command prompt type DEL [filename] where [filename] is the file you wish to delete.
   
5. Go back to Task Manager and click File > New Task and enter EXPLORER.exe to restart the GUI shell. Close Task Manager.

I've tried this a couple of times and this works great for me.