We use a version of the celebrated Larry Wall "GNU patch" program as ported to Windows.
The executable comes from the port by Karl M. Syring in his nice
UnxUtils( http://unxutils.sourceforge.net/ ) package.   We have renamed the executable
from patch.exe to vcPatch.exe to avoid conflicts.


Updated September 2007
======================
Added a manifest resource using Microsoft's mt.exe to allow running this executable
on Windows Vista without requiring prompting for admin privileges. (Vista automatically
prompts for admin privileges for executables named like *setup* *install* or *patch*.)

Given a manifest resource file named manifest.xml with contents like this...:
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<assembly xmlns="urn:schemas-microsoft-com:asm.v1" manifestVersion="1.0">
<trustInfo xmlns="urn:schemas-microsoft-com:asm.v3">
  <security>
    <requestedPrivileges>
      <requestedExecutionLevel level="asInvoker"></requestedExecutionLevel>
    </requestedPrivileges>
  </security>
</trustInfo>
</assembly>

...you add manifest.xml as a resource to an existing executable using the "mt.exe"
command line tool like this:
mt -manifest manifest.xml -outputresource:vcPatch.exe;#1