AFAIK, this is an issue with the program ran by Task Scheduler, not Task Scheduler itself. Sometimes, you can create a batch file and start the program executable. For example, if you have created a batch file with the name avscan.bat in C:\, start it via Task Scheduler using the following command:
Code:
cmd.exe /c start /min c:\avscan.bat ^& exit
This line starts an instance of cmd interpreter, that reads the c:\avscan.bat file and tries to start it minimized. Also it wraps an exit command so cmd interpreter is closed after the batch file finishes.
Also, what AV solution are you using? Usually, some AVs already have a scheduler to start a silent scan.