Last week I decided to test drive the new Windows 8 Release Preview, I did a fresh/clean installation coming from Windows 7 Professional. After starting up, it booted up fine, and everything seems to be running fine. It was not until 5-10 minutes later I experienced lagging/freezing with my system. I was able to move the mouse cursor around but I could not do much more then that I had to reboot and see if fixes it. Upon booting back it will do the same thing after 5-10 minutes. My next step to fixing the problem was to update all drivers and see if that will fixes the problem, after doing so it did same thing. So I got to a point, where I was going to go back Windows 7, because I needed a stable environment. Upon doing some research, I ran cross Microsoft forums and found a solution that actually helped me. Ever since then i have not experienced a single freeze up, running 6+ hours.
Do you have applications that start automatically when you turn on your computer and you don't want to turn them on? Disabling the unwanted applications to start automatically will speed up your boot time.