How do you go about querying running processes to find out what folders or files they have locked? (i.e. you go to eject a drive and you're told that it can't be ejected because it's in use)
I'd like to either get an "off the shelf" download, or write a .NET 3.5 app to do this (primarily a Windows question).
Process Explorer will show you this. Ctrl-F will let you search for a file and list the process(es) that have that file open/locked. You can then close that handle using Process Explorer.
There's also a command line utility called oh.exe available for download. See here for more details
http://ccollomb.free.fr/unlocker/ (freeware) has a special UI for exactly this situation.