Standby during virus scan

Well, I have an inconvenient problem-vista goes into standby, and my virus scanner scheduled for that night won't run until I resume out of standby! So then, when I want to use my PC, I can't because it is running extremely slow due to the virus scanner!

Also, if I happen to start the virus scanner while I am on the computer, as soon as I leave the computer alone, it goes into standby even with the scanner running! Urgh!

Is there an easy, convenient way to fix this? Thanks.