scheduling wakeup for system maintenance

I use Vista Home Premium on my desktop computer, I find that when I put my
computer to sleep overnight that none of the scheduled tasks run. The
computer simply does not wake up. This is true for Windows Defender, Disk
Defrag, hardware driver update programs, antivirus programs, etc. When I
wake the computer up everything wants to run and my system is sluggish until
the tasks complete. I looked all over for some way to schedule the computer
to wake up and found nothing except some off topic references to the Task
Scheduler accidentally waking up notebooks. After some tinkering I found
that you could create a custom task to wake the computer and simply display a
dialog box for a period of time thus allowing the scheduled tasks to run. I
could have simply set the tasks themselves to wake the computer but my
antivirus program uses its own task scheduler. I then set the sleep timer to
give the tasks enough time to run. What I want to know is how to set the
task scheduler to put the computer back to sleep. I would also like to know
if I could set the computer to not go to sleep during this period even if the
sleep timer is set – it would wake up at one am stay on until two thirty but
the rest of the time go to sleep after a half hour of idle time. Can any one
help?