Constant problem booting

[pd123]

Every time I boot, when I boot-up and way before WindowsXP starts, I get a black screen that says "ALERT! Backup fan not detected, press F1 to continue". I have a Dell 600sc, it has a few fans and they all seem to be working. When I press F1, it continues and runs fine. This is an annoying and persistent problem, any ideas how I can solve it?

[Markel]

Many motherboards will check if the CPU fan is spinning (in order to prevent frying the cpu). I have such a board in my old system. I recently changed the CPU heatsink/fan because the old one seemed to be failing (noises). Once I plugged in a new one, the system wouldn't boot. I had to hook the old fan/heatsink to the secondary CPU fan header in order to get the system to boot (the new fan doesn't supply the rpm signal). Once I booted, I went into the BIOS and disabled the CPU fan check (I just have to hope that the current fan never fails before I scrap this system).

Anyway, I would suggest checking your different BIOS screens and seeing if there is a place to disable the fan check. You also might find a hardware page in your BIOS that will show the fan speeds that it can sense (this might give you a clue as to why it is complaining).

Are you certain about the text "Backup fan not detected"? If it says "CPU fan not detected", it would make more sense.

You might get some help from this:
http://support.dell.com/support/topics/global.aspx/support/kb/en/document?dn=1049833&c=us&l=en&s=dhs&cs=19