unistalling programs and laptop shutting down

Cher

I recently upgraded my laptop to windows vista home premium. For some reason
I can't seem to unistall some programs now. I tried to uninstall AVG; it says
it has been uninstalled yet it is still on my computer. I also tried to
uninstall an Adobe photoshop program but it keeps saying that the uninstall
failed. Can anyone help me? One more problem; ever since I installed Vista my
laptop seems to shut off by itself for no reason. I will be in the middle of
something and the computer shuts off. Any explainations why?? What can I do
to prevent this???