Have you looked to see if you are enabling the Hibernation mode in XP?? could be that when you push the power button to shut it off,, you are actually putting it in sleep mode,, and then as soon as you open the lid,, the machine wakes up,,
plus,, I know XP is guarded better for immediate power outages with a slimmer chance of corruption, however, I would ask why you are not using the standard method of shutting down a system as oppossed to just killing the power,,
are you by chance a salesman?? On the road,, not a great amount of technical knowledge and just like to turn the PC on to get your mail or show your power point presentations to succeptible clients??
Just asking,, cuz those are the types of people that often bring their laptops in to our department,, and complain about what a piece of crap they use,, and meanwhile,, they never read, took training, or were curious to find out why things were happening..
there are a couple of my mates that love those types,, they get their laptops which are mostly Loaded up A21 thinkpads,, network them to play WC3 or Matrix, and keep the laptop for about a week,, meanwhile , the salesdude,, doesnt come down with a coffee or anything,, is crass as all HEl@,, and demands to have service provided..
truly,,, IS job security = salesmen with laptops,
Sorry for the rant,, but that sounds toooo familiar .,,
BTW: if this is not you,, just enjoy the read and check the hibernation settings,,