I have a PC with installed Windows 8. If I want to turn it on after computer sleeping (or however it is called :P), I can simply do mouse click. The problem is: my mouse is really sensitive and sometimes the computer turns on when I put something heavy on my desk :P But the biggest problem is that when I forgot to shut down my computer before going to bed, it can launch my PC in the middle of the night (no, I don't have any pets)
So, how can I turn this feature off?
Whenever you place your computer in standby, simple events such as packets from the internet, activity through USB devices and even a timer in the bios can wake up the pc from standby. Additionally, windows update and other system events can also bring a pc out of standby. So the question really becomes, are you sure that its just the mouse that you want to fix or is it maybe better to go for a solution that won't get your pc out of standby unless you hit the powerbutton switch?
Lets assume you want this solution. Instead of making your pc go to standby, make it go to hybernation instead. This will save the content of memory to harddrive and then power down the pc. When you fire it up again, it'll load the content of the memory back into the memory and resume windows where you left off. The advantage of this is, that nothing external can get the pc out of hybernation, and it does not cost any power while being in hibernation either.
There are many forms of hibernation. For example, there's a hybrid standby option which sort of does this, but keeps the pc on. You don't want this. Depending on the bios setting, Sleep can either put the pc in a standby state or hibernation state. Given that by default its set to standby, you don't want this either.
You can change how it goes to standby/hibernation from the Power Management options.
