Question : how to determine "drive in use"

I am trying to run a USB drive firmware update program, but I get the message "Drive in use". Is there a way to figure out who (as in shared user) or what (as in program) is using a drive so I can notify/skill them/it?

Answer : how to determine "drive in use"

Try Process Explorer: http://technet.microsoft.com/en-us/sysinternals/bb896653.aspx

That will list all running processes.  Within the Procmon application, select Find -> Find Handle or DLL.  You can then search for open handles on the USB drive, which should lead you to the offending application.  (You may also be able to force the handle closed by right clicking on it; this can cause system instability.)