Thanks to all who answered, I tried all the suggestions and one or all must have worked. Now my PC doesn't get woken up in the middle of the night.
Thanks again to all!!!
I'm new to Widows7 and now after 3 weeks the PC starts up in the middle of the night, the only way I can stop it is to turn off the power point. I've been looking at all sorts of things in the 3 weeks and I must have ticked the wrong box somewhere. Can anyone give me a clue where to look to fix...