Dagrev:
Here is what I have done in the past by setting priority's on via task manager this may solve the problem on start up for you.
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1
Right-click on the Windows task bar along the bottom of the screen and select "Start Task Manager." Alternatively, press the "Ctrl," "Alt" and "Delete" simultaneously and select "Start Task Manager."
2
Click on the "Processes" tab to see a list of all the currently running processes. To find processes belonging to a particular application, click on the "Applications" tab then right-click on an application and select "Go to Process."
3
Right-click on the process whose priority you want to change, then select "Set Priority" from the menu. A new sub menu appears listing the six priority options available, ranging from "Low" to "Realtime," which is the highest priority. The default option is "Normal," which is in the middle of the priority range.
4
Close the Task Manager once you have changed the relevant priorities. Change the priorities of the selected processes at any time by running the Task Manager again
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In essence this will give Avast IS priority on start up and cut down on time to boot. Also I would check the processes that are running, if there is a high usage an the processes is not needed you can disable the start up on a given process. Hope this helps