Thank you Elizabeth, it looks like a little great tool once you get the hang of it!
Yes, as it often happens to many tech developers (yours truly definitely not excluded

), the author tends to omit whatever looks too obvious -
to him 
.
However it doesn't really take long to come to terms with it: a bit of trial & error, a modicum of patience and a few
"how would I do it were I in his shoes?" do the job easily enough.
A few points that might come in handy for those pessimists who, like me, prefer to be on the safe side should the updates vanish from the web after April the 9th:
- Being a portable, the program stores the cache sub-folder with the updates in its own folder (the one where PortUp.exe resides). No immediate way to save the updates elsewhere.
- Once it determines which updates are required for your system, it must download them. Before starting the download
select them all (tick their boxes) lest eventually you find in the cache only the few you haven't installed in your system. Leave out only the ones you're sure you don't want and never will. On my system (XP with SP3) they take about 1.75 GB all together, thus don't let the 15 GB mentioned on the web page scare you.
- Apparently if you want a complete cache in order to update a freshly installed system,
all the updates need to be downloaded, if only once - no one is taken directly from your system, even though they are cached also here. The complete download takes quite a while so be sure to have a good book handy.
- I haven't tested it yet but when it comes to installing the cached updates on a new system, the web site states clearly that you may select the ones you want - no need to install all of them and then remove the unwanted ones.
- Although they look somewhat like command buttons, the controls on the second line from top are actually labels. Clicking on them only alters the order the corresponding data are displayed in. The controls on the first row from top select the action (phase) you're about to execute. The one button that really runs the operations is the "Start" button in the upper right corner.
- The definitions for Microsoft Security Essentials just won't download, period. Whether you want to panic or not because of that is a personal issue - personally I never missed them.
Good luck!