Avast features a great alternative to scanning in Safe Mode - the boot-time scanner. This feature performs a full Avast scan of your system based on simple parameters (prompt, delete all, scan only, etc) before Windows boots. This prevents the squirmiest worms from self-proliferating. I recommend running the boot-time scanner twice in succession, followed by an ordinary full system scan within Windows.

Pasted from the help docs:


Scheduling the Boot Time Scan

Click on the Menu button.
Choose Schedule Boot Time Scan.
Doing so displays a dialog allowing you to schedule virus scanning.
Check Archives, if you want scan all the archives.
Specify whether all the disks or just a specific folder should be scanned.
Select Advanced options for scheduling details.
Select how to automatically process infected files.
Choose how to automatically process infected system files.
Click the Schedule button to confirm the settings.