Hi
I’m new to Avast having changed from AVG after several recommendations 
However one thing I have noticed is that now whenever I launch a programme e.g. Firefox it takes much longer to load and the little blue ball is spinning. Does Avast scan every programme I launch? and if so can I disable this? Sorry if this has come up before but I tried searching with no luck …
???
If you have Avast 4.1, I suggest you start with updating to 4.5 beta.
Does Avast scan every programme I launch? and if so can I disable this?Yes, that is what a on-access scanner is supposed to do. Disabling this will mean you will disable your protection. But you can add applications to Avast's exclude list. In that way they will not be scanned by Avast. But if one on the exclusion list will get infected, you won't notice it !
Another possibility is setting the security level to ‘Normal’ instead of ‘High’.
You won’t scan every read/open/created file but only the executable viruses 
It’s difficult to find an equilibrium between the security and the performance.
What kind og computer do you got man , you wish to check slowlines , try kaspersky real time scaner , avast is 10 times faster