What does this error message from the Avast! log mean, please.
04/12/2004 11:59:46 am SYSTEM 1928 AAVM - scanning error: x_AavmCheckBootDirectEx: avscanScanReal of *BOOTA failed, 00000005.
04/12/2004 1:05:18 pm SYSTEM 1924 AAVM - scanning error: x_AavmCheckBootDirectEx: avscanScanReal of *BOOTA failed, 00000005.
If you have searched the board you would found that this happens when you ask for a full scanning (all parts of your computer) and the flooply is not on its drive, so, avast can’t scan the boot sector of A: 
I did have a look round, but as I didn’t know what I was searching for, that’s not too easy. Thanks for the help anyway. Have you any ideas why it showed up on a date when I didn’t do a full scan, but didn’t show up one day later when I did do a full scan (scheduled) with no disk in Drive A?
Regards
Bob
You’re doing difficult questions ;D
Sometimes computers are not deterministic 
Sorry, I don’t know the answer. Anyway, nothing to worry that much 8)