If a file is in use by a program or Windows itself, then it cannot be deleted as long as the program is using it. The problem is that some of the files seem to be always in use by some or other programs and thus it becomes very hard to delete them. But now you can use the Free Delete on Boot program from TrishTech.com to delete such stubborn in-use files on the next boot of Windows.
You can download Delete on Boot program from the download section of TrishTech.com. The program is completely portable and standalone application. It can be run on Windows XP, Vista, 7 and 8. You can download the ZIP archive, extract the files to a folder and run DeleteOnBoot.exe from there. The GUI of the application is very simple.
All you have to do is click on the … button to browse for a file on your hard disk that you want to get rid of. You can also type in the name of the file in the text box. After this, you can click on the Delete on Boot button to set that file to be deleted on the next Windows boot. It will show the information message box that the file has been set to be deleted.
Now all you have to do is reboot your computer. Upon the next Windows boot, Windows would automatically delete these files. You can check that the files have been deleted by browsing to the folders where they once existed.
You can download Delete on Boot from http://www.trishtech.com/downloads/.