From http://www.portableupdate.com/default.aspx:
“Portable Update is a windows-base tool for updating a Microsoft Windows computer in a isolated environment.
[…]
Once the update is stored into the cache folder , the program will use standard Windows Update API services to update your computer.”
I tested the program on a Windows 7 virtual machine. It worked fine. It needs the built-in Windows Update service to function, and will enable it if it’s disabled. According to the author, searching for updates in offline mode may find fewer missing updates than using online mode.
Similar program: Windows Update MiniTool.