I figured out how to schedule a scan using the avast! shell extension program, ashQuick.exe (the program that kicks in the scanner when you right-click on a file and choose "Scan" from the popup menu), and the Windows Task Scheduler. I thought I'd share this trick with others. Here's how to do it:
(NOTE: These instructions are for Windows XP and assume Windows is set up to use "single click" to open items. I would assume the steps would be similar for other versions of Windows.)
* Go to Start > Programs > Accessories > System Tools > Scheduled Tasks
* Click (or double-click) on Add Scheduled Task
* In the wizard that appears click Next - a list of programs will appear
* Click Browse and navigate to C:\Program Files\Alwil Software\Avast4 (or whatever folder in which you installed avast!)
* Click (or double-click) on the file ashQuick.exe
* On the next screen give the task a name of your choice and choose how often you want it to run and click on Next
* On the next screen choose the appropriate scheduling options ( preferably at a time when you're not using your computer, as scanning uses up a lot of cpu power ) and click on Next
* On the next screen enter the user name and password for the Windows user you want the task to run as, then click on Next.
* On the next screen check the box for the option "Open advanced properties for this task when I click Finish", and then click Finish. If you don't enter a password a warning may pop up telling you that the schedule may not run. Click the OK button and check the " run only if logged on" box at the bottom left of the next screen.
* On the same screen, in the "Run" box, the path should be "C:\Program Files\Alwil Software\Avast4\ashQuick.exe" C: or whatever drives you want to scan . Multiple drives must be separated by a space, such as "C:\Program Files\Alwil Software\Avast4\ashQuick.exe" C: D: E: F:
* Click OK
* In the Scheduled Tasks window, from the menu, click on Advanced and choose "Start Using Task Scheduler"
* To test your newly created task, from the Scheduled Tasks window, right-click on the task's icon and choose "Run" from the popup menu. If the scan doesn't begin correctly you'll get an error message. The problem is most likely in the scan path (missing quotes or something like that.)
* Close the Scheduled Tasks window
Keep in mind that this is just a "quick scan" and I'm not sure with what sort of depth that ashQuick.exe scans, but it beats nothing at all.
I don't know if there is any way to pass other parameters to the ashQuick.exe program for various options like scanning depth, what to do if a virus is encountered, etc. If anyone has any info on how to pass other parameters please feel free to add the information to this thread.