I want to run a full scan in the middle of the night when no one is using the machine (XP Home) but I want to leave the machine in Standby to save power. Is there a way to do it?
There is no way that I know of that you could accomplish this in Standby mode to save power. The computer obviously needs to be on for the scan to occur at the designated time and you can choose whatever time you want the scan to occur. I have mine set to scan Friday morning at 4:00 am
Officially no there is not any way of doing that but one customer made up a tutorial that may work for you, however it has to be VirusScan v16.8 or higher and having XP limits how high you can go with McAfee versions, so I would check what version of VirusScan you have onboard before even attempting it. (Open SecurityCenter and then click About).
I dunno, if this is XP it might work. Depends on how the power settings are configured, if hibernate is disabled or set for a very long time but standby is enabled ... yes, it might work. Everything's still in memory in Standby, the system clock is working, and if there's something's scheduled for a certain time then it might be sufficient to issue a wakeup call to the system. There's only one to find out and that's to set up a test. Add something in Scheduled Tasks for say an hour ahead - something that will be immediately visible so you know when it starts - then go into Standby and wait.
I might try this later myself.