OK, some additional news...
Today, I found a friend's computer running Windows 7, and I could use it for whatever I wanted.
So I created a new Rescue Disk under Windows 7.
First, as far as I can remember, my computer (running Windows XP) did download very few things before creating the Rescue Disk. The one running Windows 7 did download the whole "installation kit" (about half an hour with a pretty good internet connection - the peek speed at my friend's home is around 1,6 MB/s). For further information, on my XP computer, the WAIK is yet installed, perhaps it's the reason why so few things were downloaded the day I created the first Rescue Disk.
Then the Rescue Disk creation process took place, and the resulting iso file was about 245 MB (the iso file created with Windows XP was much smaller).
I tested the Rescue Disk on this Win7 computer, and the result was fine.
But I wonder...
The "installation kit" is a huge thing. The free space on the hard drive is now 3,5 GB less than before starting the procedure (and this doesn't include the iso file, which was created in a different partition). Perhaps Avast! could create an iso file on it's servers, "ready to use", withe the latest definition updates, so the user would have to download only the iso file? That would save a lot of things : time, space on my hard drive, internet flow, and so on... and it's always possible for Avast! to reserve the ability to download the iso file on computers running Avast! software(s).
May somebody escaladate this opinion ? Or tell me where I can say them directly ?
Thanks in advance