If no other way works, put the drive in another computer and delete it that way.

If you already know the path to the undeletable file, please skip to Step 7

1. Click on Start, Search, All Files and Folders
2. Type the name of the undeletable file in the box shown
3. Make sure the Look In box shows the correct drive letter
4. Click Search and let the computer find the file
5. Once the file is located, right-click on it and choose properties, make a note of the file location. Usually this is something similar to

c:\windows\system32\undeleteablefilesname.exe

6. Close the search box
7. Click on Start, Run, and type CMD and Press Enter to open a Command Prompt window
8. Leave the Command Prompt window open, but proceed to close all other open programs
9. Click on Start, Run and type TASKMGR.EXE and press Enter to start Task Manager
10. Click on the Processes tab, click on the process named Explorer.exe and click on End Process.
11. Minimize Task Manager but leave it open
12. Go back to the Command Prompt window and change to the directory where the file is located. To do this, use the CD command. You can follow the example below.

Example: to change to the Windows\System32 directory you would enter the following command and Press Enter

cd \windows\system32

13. Now use the DEL command to delete the offending file. Type DEL <filename> where <filename> is the file you wish to delete.

Example: del undeletable.exe
14. Use ALT-TAB to go back to Task Manager
15. In Task Manager, click File, New Task and enter EXPLORER.EXE to restart the Windows shell.
16. Close Task Manager

maybe its a virus? back up your files and reformat..
sometimes thats the last option...

As previously mentioned by other users try Unlocker. Its really good

Use Unlocker. Simple and quick.

Use Unlocker !

Even though I have got this message before I have deleted it but Unlocker is a new tool for me. I'm keeping it by the way thanks for the link.

agree with rep, it easy and simply to delete locked files or folders. i post article in <url snipped>

why are ppl still adding "advice" to a question posed nearly a year ago??