Installation Too Big

Using only File and behavior shields my installation is 505MB Why so large for only two shields?..The only thing I dont like about Avast

what avast do you install? … and build number?

That will change when 2014 is released as it will use a stub installer and only download what is required

I don’t know what avast version you are using, but my figures aren’t even close to yours and I have all but two (IM and P2P) shields installed.

The virus definitions database (avast\defs folder) takes up a great deal of this 140MB on my system and that is variable as new definitions are added creating a new sub folder with the contents of of the old one combined with the latest incremental update. Avast periodically does house keeping removing the old defs sub-folders. So if you had the current defs version and the previous version (pre-housekeeping), that could vary by 140MB up or down (in your case).

My XP install of 2014 Beta 2 uses 250 MB at \program files\AVAST software

Did you update Avast installing the new version over the old one? I had the same issue recently (installation was about 500MB).
Just in case, try clicking the Program Update button inside the GUI (Maintenance/Update) and then rebooting your system.
It did work for me - don’t ask me why, I have no idea, it just worked.