This morning, when I powered on the pc, the boot process froze with the Asus P4P800 screen displayed. After a while, I heard a sort of low-key whining. After several attempts, I dropped everything and went out. An hour and a half later, I tried again and lo and behold I went past the Asus screen and got a message from AMI saying "Overclocking failed". I went through every single item in the BIOS. Nothing had changed since my first successful installation a year ago. Overclocking was still at "standard" (I never did try to fire things up over the past year). From then on, everything worked fine. Is there an explanation somebody could provide?

If I hold down the power button to shut down my mobo (when i'm in bios or during POST), the motherboard thinks something has failed, and gives the overclock failed message (even if you're not overclocking). It's just a general error message. Change a setting, then change it back...save, and reboot. Since you heard a whining...where did you track the sound coming from?

I had trouble in locating the whining. It appeared to be coming from the motherboard (!). The fan on the chipset was okay. I checked the 4 disks one by one and they were also okay. The most reasonable origin is the Power supply. It did produce a louder whine a few weeks ago which would come about every now and then but without preventing the system from operating. That's why I will be installing an Antec I just bought to replace the cheapish power supply which came with the box. I have a strange feeling that the power supply is behind all this, even though my first unsuccessful power on I described above was carried out after 8 hours of total power off. After a full year of running this pc which I assembled from scratch, I never ran into this phenomenon.