I find it.
When you use Avast AV from your bootable Avast! Rescue Disc CD ( the first item on the vertical menu), at one point, it shows 2 options. Rather download the latest virus definitions vsp or to look for vsp in a specific repertory of a Hard Disk you have.
I wont to download the VPS but a warning box sais first that the connection to the Internet is not established and asks me if I wish to connect.
I clic yes. Then a dialogbox opens and asks me the path to VPS file.
Search for
C:\Program Files\Alwil Software\Avast5\defs\...
In this repertory you've got two repertories named of the latest date of virus definitions downloaded.
Today they are named "12031100" and "12031100_stream".
Select "12031100" and it loads or downloads and stays in memory.
Then, only, you can start your scan with updated virus definitions.
I just wish you not to have to use it.
@ RegB
The windows installation of avast seems to use .vpx files and there are no .vps files anywhere on
my C: drive.
I have a recent up to date 400.vps file here: C:\Program Files\Alwil Software\Avast5\defs\yyMMdd00\400.vps
Don't you ?