Sometimes you may want to delete a file, but find this isn't possible because it's locked. Some tools try to help out by unlocking the file, but this is a dangerous process which risks crashing your PC. Reboot Delete File Ex offers an alternative: point it at the offending file and it'll ask Windows to delete it when your system next restarts.
There's nothing complicated to this process at all, but the program still requires installation, most probably because this gives it a chance to equip your PC with a toolbar. If you're not interested then watch carefully during setup, and click "Decline" as appropriate.
With that out of the way, click "Add Files" and choose whatever files you'd like to remove. Click "Delete" to mark them as unwanted. And if you'd like to restart now, click "Reboot PC" to do so. (This isn't necessary, though. Feel free to close Reboot Delete File Ex, reboot whenever you like, and your chosen files will still be deleted.)
If there's an issue here it's that Reboot Delete File Ex doesn't allow you to view any files which are currently marked for deletion. If you choose two files, close the program, then wonder if you've made a mistake, say, relaunching Reboot Delete File Ex isn't going to help. It won't show you the files you selected last time, and there's no way to change your mind, to say you don't want to delete them, after all. If you want to do this then you'll need to venture into the Registry (HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\PendingFileRenameOperations), and even then it may not be straightforward.
What's more, just because you're not unlocking a file, doesn't mean this is an entirely safe technique. If you accidentally delete something important then you could still crash your PC, so Reboot Delete File Ex should be used carefully, and as a last resort - if you must use it at all.
Reboot Delete File Ex offers a useful way to delete locked files, but there are risks involved. Only use the program when it's absolutely necessary, you're completely sure it's safe to do so, and you have a full system backup to hand.