Windows Vista stuck on installing updates when powering off.?

I am using Windows Vista Home premium on another computer. I have encountered a problem however because when powering off, it will stay stuck on" please do not power off or unplug your machine, installing updates 1 of 4". This message will be there for hours at a time before letting me boot back up again as i have had this problem for the past week. Is it safe to perform a shutoff by the power on so that i may proceedingly reinstall vista.