I'm posting this for public notice. 

I have a Vostro 200 that started to randomly hard shut down on its own without warning. After messing with it for a couple days thinking it was a software issue, I decided to open the case. Turns out the CPU fan bracket had cracked off from the mount screws on one side. The bracket is part number cn-0jy167-69861-76m-04a9 rev a00, I assume Dell uses this on other model PCs.

PS The warrenty just ended on this machine as of 8-30-08.