Vista - not remembering appearance settings

I am running vista home premium and for some reason for the last 2 days it
wont remember my appearance settings. Everytime i switch on my laptop it has
changed from windows aero to windows classic. I did a system restore to back
to one week ago and its still doing it. Ive even cleaned out the registry and
done a virus check but it keeps doing it. Its really frustrating now that
everytime i boot up my laptop i have to change its apperance back to the way
i want cause it wont remember my previous settings. Anyone have any ideas on
how to solve this??