I have been using a remote desktop app called iTap on the mac, but have recently run into problems with my Media Center waking up right after going to sleep, fortunately there are some very useful tools in Windows to diagnose the problem…
To find out what event/device woke up your Windows from its sleep state, go to command prompt (type cmd on the Run/Search box and press ENTER), then type this: powercfg – lastwake
To get the most detailed info (and probably easiest) on the device that wakes your Windows up during the sleep, type: powercfg –devicequery wake_armed
The cause turned out to be iTap, which shows the status of your machines, but in doing so transmits a magic packet which wakes the machine up, which is useful unless you want it to remain asleep.
I hope they add a preference option to manage this setting, as the app is otherwise excellent.