This blog is about Linux but by day I'm doing the "dark force" type of things :). I'm a Microsoft SQL DBA, go figure, anyway. I had a problem with an old backup file being locked by a process and wouldn't get deleted either by VB script job or Enterprise manager utilities. I needed to identify what process was holding the file. I fired up Process Monitor, a little utility that identifies pretty much more info than I'd ever need. Lo' and behold, there was my file being locked by Tivolli tape backup process. I highly recommend sysinternals suite that you may download from SysInternals.
The suite is huge and I haven't used many other utilities, so if you do get to use others, please leave a comment on what were you trying to do and how well it worked out for you.