Computer Keeps Turning Itself Off And Also Resetting Date And Time

The problem I am having is that whenever I log onto my computer, I can see that the date and time at the bottom right of the screen always seems to reset to 31/12/2006. I always try to fix this by going to the option where you can synchronise the date and time with the Windows server time, however, this doesn't always seem to work.Another problem I am encountering is that the computer itself seems to be cutting out at different times, for example I could be 98% complete into a full system scan with Kaspersky 2012, but the computer suddenly cuts out, this would also be the case when browsing the internet or completing some Word documents. One other thing to mention as well is that since these problems have occurred, whenever I turn on my computer, I never have to press the power button on, as it seems to turn itself on whenever I switch the power supply on. This is also not normal.