My Avast! 4 Home edition’s help File shows that the VRDB is updated each 3 weeks by default, and help file states that that value may be changed by editing avast4.ini. But I fail to find the related parameter in avast4.ini.
So, could any experiecned would like to teach me to change the default value (e.g. 1 day or 6 hours ecah) and also how to restore the infected file by VRDB if necessary?
Thx!!! 
http://forum.avast.com/index.php?board=2;action=display;threadid=1647;start=msg15899#msg15899
BTW if you do a forum search for the word RunInterval you will find tons of dicussions about changing this entry. The bottom line is that you shouldn’t change this entry unless you know what you’re doing exactly…
Thanks for your help and opinion. Actually, I have tried to search the solution by another key work “VRDB”, but returns lots of searching result.
But, anyway, thx for your help again.
Technical did an excellent thread explaining the ini files, and it’s in there somewhere. Sorry I don’t have a link to it handy, but I’m sure someone else will be happy to jump in and supply it.
With specific regard to VRDB update-frequency, you’ll find you’ll have to add a new line to the [VRDB] “paragraph” of the ini, since it’s one of many settings where avast uses a default value (in this case 3 weeks) if there’s no specific reference to it in the ini.
Thanks for your words Mike 
The link was posted by Vlk here (thanks for quoting me Vlk ;D)
As Vlk said, do not change the frequency of the VRDB too a very low value. It needs the ‘right’ information about the exe files and not ‘too’ updated one. With errors, you could (in some cases) not be able to recover the right data as you fill VRDB with the wrong ones.
Specially if you install/uninstall a lot of softwares, let the default value there 8)
Thx for the opinion of Mike and Technical again.