One of my favourite tools for linux is lsof - a real swiss army knife!
Today I found myself wondering which programs on a WinXP system had a specific file open. Is there any equivalent utility to lsof? Additionally, the file in question was over a network share so I'm not sure if that complicates matters.
Try Unlocker.
The Unlocker site has a nifty chart (scroll down after following the link) that shows a comparison to other tools. Obviously such comparisons are usually biased since they are typically written by the tool author, but the chart at least lists the alternatives so that you can try them for yourself.
Try Handle. Filemon & Regmon are also great for trying to figure out what the duce program foo is doing to your system.
If you right-click on your "Computer" (or "My Computer") icon and select "Manage" from the pop-up menu, that'll take you to the Computer Management console.
In there, under System Tools\Shared Folders, you'll find "Open Files". This is probably close to what you want, but if the file is on a network share then you'd need to do the same thing on the server on which the file lives.
One equivalent of lsof could be combined output from Sysinternals' handle and listdlls, i.e.:
Unfortunately, you have to "run as Administrator" to be able to use them.
Also listdlls and handle do not produce continuous table-like form so filtering filename would hide PID.
findstr /c:pid: /c:<filename>
should get you very close with both utilities, thoughHere we can see that gvim.exe is the one having this file open.
Use Process Explorer to find the process id. Then use Handle to find out what files are open.
Eg handle -p
I like this approach because you are using utilities from Microsoft itself.
In OpenedFilesView, under the Options menu, there is a menu item named "Show Network Files". Perhaps with that enabled, the aforementioned utility is of some use.