Now it is working. For those interested I appended vb script 
I use to scan all local disks.

<<<<<<<<<<<<
Set shell = WScript.CreateObject("WScript.Shell")

'Scan
shell.LogEvent 4, "VirusScan started"
q=""""

'using defined task
ScanCmd = q &  "D:\Program Files\Alwil Software\Avast4\ashCmd.exe" & q & " /@=" & q & "ScanAllDisks" & q

r = shell.run(ScanCmd, 0, true)
if r > 1  then
  shell.LogEvent 1, "VirusScan failed", 2
end if
if r = 1  then
  shell.LogEvent 1, "Virus found", 1
end if
shell.LogEvent 4, "VirusScan ended"

'Hibernate
shell.run ("rundll32.exe powrprof.dll, SetSuspendState")
<<<<<<<

1. I defined a Windows XP scheduled Task for the scirpt.
2. I checked the task property "Wake the computer to run this task".
   And enabled the realtime clock (RTC) in the bios.
3. The script uses a Avast! task, so it shows up in Avast's session log.
4. I had to create my own Avast! task "ScanAllDisks"  because I 
   could not get the builtin task "Scan: local discs" running using ashCmd