I have a friend who's wife's computer is having a curious issue. It's an old Dell Optiplex GX270. She uses it mainly for surfing and emails. The CPU cooler fan died and the computer shut itself down with a thermal warning notice. I replaced the fan and when the XP load page comes up the computer shuts down, again showing a thermal alert. The fan is actually bigger than the original so it is providing sufficient cooling. However, when I boot to safe mode, the computer runs fine. It doesn't shut down. Any thoughts as to what might be going on with it? Thanks for any help.