Windows vista problem

since when r u getting this message
try doing a system restore if the problem started recently
if its a dell
the moment you power on the system press F8
you will get system's advanced options
use up and down arrow key
highlight safe mode
press enter
if will ask about your operating system
press enter again
when you get user name options click on administrator
you will get a pop up which says
to run windows in safe mode press yes and to run a system restore press no
it winn only happen if you are using win XP
press no and you will get system restore screen
choose a highlighted date the date in BOLD