I found this nice command line tool of Microsoft's that will make a patch file by comparing two files which can be used with their command line patching tool to create the 2nd file.  This works great for patching an executable that is large.

The patcher works on Windows XP without the SDK installed.  But the SDK must be installed to get the command line tools you need.

The command line tools you will need from the SDK are called mpatch and apatch and are in C:\Program Files\Microsoft Platform\SDK\Samples\SysMgmt\Msi\Patching.

Here is the download:  Platform SDK


I found this by reading this blog entry.