Windows Update is easy to use and generally works well, but there can be problems. What if your target computer has a really slow internet connection, for instance? Or perhaps no connection at all? Or what if you need to equip several brand new PCs with a host of Windows updates, without downloading them all individually?
Portable Update offers one potential answer. The program can search your target computer for missing updates. Download the relevant patches from that computer or any other and they'll be stored in the Portable Update cache. Finally, those cached update files can be installed on that computer, or any other, without having to download anything else.
While this sounds straightforward enough, there are complications. Portable Update is very small itself, for instance (a 591KB download), but in order to work it must first download some 83MB of files from Microsoft. You only have to do this once, of course, but if your internet connection is slow then expect to wait a while before you can try the program out properly.
The Portable Update interface isn't exactly intuitive, either. There are no menus or significant right-click options to show you what's possible, just a series of tabs and a Start button. If you click "Start" in the wrong place then there's no message to explain what you should do instead: nothing happens at all. And there's no help with the program, either. (There is some online documentation, but if you happen to be using the program offline - which is presumably quite likely - then this won't help you much.)
These aren't fatal issues, though. Portable Update's operation may not be too obvious, but it's not difficult, either, and once you've learned the basics - which will only take a few minutes - you'll be ready to take full control over the Windows process, even when there's no internet connection available.