There is a utility called MV that comes with the NT res kit:

Usage: mv [/x [/d]] file1 [ file2 ...] target
/x dont save deleted files in deleted subdirectory
/d specifies to delay the rename until the next reboot.


Rename a currently used system file (.dll) to something else and then MV /x /d newfile.dll currentfilename.dll and one the next reboot, the new file replaces the old one.

HTH

cj