OK, I've removed the entire record:
autocheck aswBoot.exe /A:"*" /L:"English" /archives
and now it's ok, no more Boot-Time Scan.
THANKS!!
The first BTS has been scheduled by the pop-up message appeared at the end of installation.
This asked if I want schedule a BTS at the next boot, and I've pressed "Yes".
But during the BTS my pc was shutdown, and at the next boot the issue is started.
Just, my computer is a notebook and it was power plugged;
maybe the BTS is not recognized as an activity, so it was started an Hibernation procedure.....but....it's strange.
I tried to schedule a BTS - check the registry key - unschedule the BTS, and works properly: only aswBoot.exe /A:"*" /L:"English" /archives was added and removed.
I don't know, I've got another pc with Avast 4.7 Pro and WinXP and I've never experienced this kind of problem; it's true, I've never seen a computer hibernating, during a disk scan; maybe Vista added the "autocheck" during the system check at reboot.
Thanks again for the help.