And also try to make sure that you don't have so many things running on startup.

Try simple things first - check cpu for dust, run a virus scan, check power supply, check other hardware such as memory

I too advice you for a fresh install. Also, Check registry files, make sure they aren't corrupt. Make sure you've defragged your disk and checked the disc for errors

One more thing could be, over time, as you add more and more programs to your computer, many of these applications automatically add themselves to your Windows Start-up folder.

Additionally, these...