My HTPC wakes up every day at 11:23 AM

And I can't figure out what program is doing it. Task Schedulers' UI sucks. Help?

Are you sure it isn't Media Center downloading the newest Guide information?

Mine wakes up at 3:00 Am every night to download it and any Windows updates, then goes back to sleep. Might be what's happening to you.

I use XBMC and have WMC disabled

Well, in that case, I don't know. Unless it's Windows updates, or your AV program updating...

As soon as I wakes up I power up my TV to see what it's doing, but it doesn't seem like anything. CPU stays under 5% and the computer will go back to sleep in 20 minutes after it wakes up, which is what I have it set to.

There has to be a way to list every task by time, is there not?

Does anyone know of a way to organize all tasks by time?

bump

Windows performs many tasks at night, including backup jobs, degragmenting hard drives, and more. These are typically the root cause of the wakeups. You can begin troubleshooting by opening an elevated command prompt* and typing powercfg /lastwake to see what woke up the computer last.
*To open an elevated command prompt, type cmd into your start Menu, then press Ctrl-Shift-Enter.