Here is a step-by-step walkthrough of how I schedule scans with Avast 4 Home. These scans are not really necessary since Avast is constantly protecting your machine; however, you can never be too safe.
I am running Windows 2000, so the walkthrough might differ slightly on your PC.
To schedule a scan with Avast 4...
-Go To Scheduled Tasks
Start -> Programs -> Accessories -> System Tools -> Scheduled Tasks
-Click Add Scheduled Task
-Browse to your Avast Directory (it should look something like...)
C:/Program Files/Alwil Software/Avast 4/
-Click on ashQuick.exe
-Choose how often you would like to perform this task (I scan weekly) and click next
-Choose the time/day/date etc. of when you would like the scan to occur and click next
-Enter your logon password. If you do not have a logon password, just click next.
-Check the Open Advanced Properties box and click Finish
-Under the Run Command Line, after the quotes, type c:
It should look something like...
"C:\Program Files\Alwil Software\Avast4\ashQuick.exe" c:
This tells Avast scan the C: drive
-Click OK and Retype your password if necessary