Where is the file located? Inside C: drive? Then only the user with admin rights can delete it.
If the file is somewhr else, then check which process if locking it in Taskmanager and kil that process. If not able to identify the process, download lockhunter, replacement for unlocker since it doesnt work in Win 7 and unlock the file or folder and delete it.
LockHunter is a free 64/32 bit tool to delete files blocked by any processes
Also, when you open run command, by default it doesnt execute with admin privileges. Go into accessories and then from there execute command prompt with run as admin.