Vista - Task Scheduler Problem

Task Scheduler wakes the machine from sleep to run the scheduled task. The
task starts, but the machine goes back to sleep within a minute leaving the
task partially complete.

Is there any way to add commands to the task that will disable sleep mode
while the task is running, then enable it when the task completes. I have
tried the powercfg command to set the sleep time to 'never' (0) then back to
60 minutes at the end of the task, but that didn't keep it awake.

I tried this for Norton as well as for a script that backs up files to my
server and couldn't get either to run properly.

Mike