Just bought new components to re-build computer.
Purchased:
Asus P4B553-V motherboard
Intel P4 2.4 gig 533mhz
DIMM PC2100 DDR 512 non-ecc RAM
Antec ATX box with 400w power supply

Ok, so we set the whole thing up (read instructions over & over). When booting the computer we get the error "Hardware monitor found an error. Enter power set up menu for details." So we go to BIOS & see that the 'Power fan speed' is highlighted red at only 1600. The motherboard minimum requires at least 2000.

We had an additional brand new Antec 350w power supply that we tried hooking up, but got the same rating. What is going wrong here? Any suggestions? How can this be fixed? Thanks for any input.

If the RPM reading is accurate, this may be an indication that the power supplies have automatically variable speed fans. The better Antec PSs have this feature. Does the RPM reading increase after the system has been running for a while? Reply with model numbers of PSs.

If both power supplies are brand new and in working condition, just turn off the dang hardware monitoring. At least the one for the power fan speed. Just mess around a bit and see if you can turn it off, should be pretty straight-forward. If you're worried about damaging something, don't be. You can always go back into the BIOS and set everything back to factory defaults if you mess up.

Ah yes, you have one of the high-end Asus mobo's. Those things are designed to handle high-speed parts, which usually also means hotter parts. Most of the fan speed related settings are there for heat protection, so you don't burn anything out, but in this case, the power supply is working properly so turn off that monitoring setting. Keep the others.

I concur.......

Power supply is Antec model # SL400. Came in Performace II series Soho file server case.
We let the computer run for a bit to see if the rpm would raise after getting hotter - the highest we got it to was in the 1700's. (But if it did raise to above 2000, would we have to turn computer on a half an hour before we wanted to use it in order for it to 'warm up' each time?)
Then after re-reading more threads here, we figured out that the power supply has a smart fan. We tried disabling the monitoring in the BIOS, by switching it to "ignore" in the power menu, but still no luck. I'm still not positive if we've done all we can in BIOS, but I don't know what else to do.
Today we're gonna see if we can buy a new power supply without a smart fan in it and hopefully we can return one of the other power supplies that we have. Looks like we'll have to keep the other, maybe I can use it with the old P3 motherboard to set up a 5th computer...
Another question this raises in my mind is - Do smart fans not work with P4 mobos? Why would this be as they are both the newest on the market, why would they be uncompatible?

How about removing the power supply's tach connector from the motherboard and see if the alarm goes away? I know that creates a 0 RPM condition, but maybe there is other monitoring circuitry that knows if a tach is connected or not, and adjusts accordingly. I think many power supplies do not have a tachometer output, so I would not think it is a requirement for the motherboard.