Determine which process has a file locked - Windows 7

Are you getting that "can't delete" or "can't rename" a file because it is in use message.  On Windows 7 you can use the Resource Monitor (just type the name into the Start search box to find it) to easily find out which process has a file locked.

Start the Resource Monitor and switch to the CPU tab.  Just type the file name into the Associated Handles search box and you will be able to see which processes have matching file names locked.  To kill the process, just right-click and choose "End Process".

Easy as pie and all part of Windows 7.