I accidentally enabled boot-up scan but want to disable this feature. I can’t find an option for this. Any idea how to change this as I don’t really want to have to re-install. ???
Welcome to the forums, Bugazoid ! 
A search of the forum (search button at top) produced this result:
http://forum.avast.com/index.php?topic=16566.0
Do as instructed there but unselect boot time scanning.
I hope this helps you.
Reboot to let the boot scan start and then press escape when Avast starts, boot scan is a one off only you need to schedule it every time you require it…
Thanks for that post, essexboy!
It is a one operation deal, if after you restart it does the scan that is it, no repetition.
You can also cancelled it if you don’t want it to fire on the next boot. Run the On-demand scanner, menu, schedule boot-time scan. If you have already scheduled it you will be given the option to unschedule it, click yes.
Thank you, David … that was what I meant!