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 applications can add themselves quietly to a hidden area of your Windows Start-up system (accessed via the MSCONFIG run command). In extreme cases your PC will appear completely frozen.

Limiting the number of applications loading themselves at start-up can speed boot times considerably and increase overall system performance.