Hello,I installed a Nvidia 8400 GS card in my computer it has a fan but my onboard fan picks up speed sometimes and goes back to normal I have a 400 watt power supply the card calls for more power but it runs fine just my fan speeds up will this burn my motherboard up? Thank You
Very unlikely! The 8400GS is not a power hog. The on-board fan is temperature controlled and it is normal for the fan to speed up, that it slows down again is a sign that it is providing enough cooling.
You should be just fine.