Reboots randomly

[Rich]

I've been running Vista Home Premium and I've just started having a problem
with Vista just restarting itself and all my running programs are obviously
shut down unexpectedly and can lead to problems. How do I diagnose what is
causing the problem? I have auto updates set to download and let me decide
when to install them so that isn't causing it? I don't have any other
program that would restart my computer. The only change I've made recently
was turning on the guest account so my Sister can use the computer while she
is visiting.

Thanks for any help, Rich

 

[Spirit]

You may have a Task that needs to reboot to complete.

Remove the Guest account and go back to the way you were
using it and see what happens.