fatality
Sometimes when I browse the Internet I am "kicked off" the browser (the desktop becomes active) and I have to click inside my browser's window to use it again. It's kinda annoying, especially when I am chatting with somebody and typing. I have a notebook (Samsung) with W7
chillian
From my experience it sounds like some of your external devices (a mouse, keyboard, or any other USB device such as external hard drive or a Wi-Fi adapter) has problems with drivers. Check them for any updates. If you have none of these then maybe there's a problem with the touchpad: plug in a mouse and use it instead. You should also check if you have a screensaver, maybe it simply kicks in.