I’m using Verizon’s Internet Security Suite which contains anti virus and anti spyware along with a firewall. I wish to set the system for scheduled scanning. I’m using Windows xp.

1) How often should I scan for viruses and spyware?
2) A scheduled scan won’t take place if my pc is off.
3) Will it run if the pc is in hybernation mode?
4) Any drawbacks to leaving my pc in hybernation mode when I’m not using it instead of closing down all pc stuff
4) If yes to question #3 ~ what are the drawbacks?