I have an ATI Radeon 9800 Pro since the beginning of 2005. It's been working flawlessly until recently. Whenever I power up the computer, there's this loud whirring noise for about 10 seconds. Then it gets softer and goes away. This only happens occasionally, but it's been happening more frequently (about every other power up). The noise never happens after the power up, and it does not happen when I reboot the computer. I opened up the chassis multiple times, and for some reason whenever the case is open, the noise never happens. All the fans are working when I checked them with the chassis open. I disconnected the chassis fan one by one, and the noise still occur. So I suspect it's either the PSU fan or the GPU fan on my 9800 Pro. The CPU fan turns at its own sound that I readily recognize, so I don't think that's the problem. In addition, I've been monitoring the temperature of my CPU and motherboard, and they're all fine (CPU idling around 46 Celsius, and the mobo is around 30). Even after thirty rounds of CS:S, the CPU temp is only about 51 Celsius. So, I am just wondering whether I need to worry about the noise and whether anyone else is having the same problem. I searched the forum already, and I didn't find anything obvious that's related to my problem. Please provide some feedback. Thanks.