How to prevent unwanted automatic wakeup from sleep in Windows 7

I was plagued with this problem for long. Every time I put my shiny new computer with Windows 7 RC to sleep, it will wake up automatically after some time. Now this was very annoying as I am on an Internet plan which allows me unlimited download between 2 am to 8 am. So I have automated this process so that my computer wakes up at 2 am and goes back to sleep at 8 am. This way I was saving on electricity bill and some component life too. But though I liked windows 7 much more than my XP and Vista, I had to abandon it due to this problem. But then I found the solution and here it is:

Step -1 Right click on 'Computer' and select 'Properties'

Step -2 Select 'Device Manager'

Step -3 Expand 'Network Adapter'

Step -4 Uncheck 'Allow this device to wake the computer.'

Step -5 click 'ok' and close all the windows.

Step -6 You are done.