Hi there,
Tell us about you system components, motherboard model, CPU, RAM, graphics card, external hardware devices to get a clearer picture of the problem/s you are having. It may well be two separate problems in that your MB fans, CPU fan, system fans (1 or 2 or 3) power fan and chipset fans are either controlled by the MB by voltage, or pulse width modulation, or not controlled at all and run at full speed.
A fresh (clean) install of XP-pro means usually means you have saved your data, and reinstalling the OS to a reformatted NTFS HDD volume. the Function Key F1 is for Help, either associated with the BIOS or OS, or applicationi software
If that's the case, check out the MB first to make sure it is functioning OK, and the fans are running OK.
Disconnect any external hardware devices, HDD, DVD, USB devices. Have just the CPU and CPU fan plugged in, RAM installed, your graphics card in place, and a PS/2 keyboard.
Then boot the system to the BIOS system setup. Usually the CPU fan header has 4 pins. Check the BIOS PC Health screen and it should give you the CPU fan speed. That should check out OK.
Then turn off your system, and plug in your system fans. Some fan headers are 3 pin, sometimes there is a 4 pin fan header. Make sure the fan 3 pin connectors are inserted with the key matching, and if there is a 4 pin system header, the 3 pin connector is on the left pins 1,2,3.
Reboot your computer to the BIOS system setup screen, physically confirm all fans are spinning, and they are recorded on the BIOS PC Health screen. If you have multiple system fan headers, sometimes Gigabyte doesn't show all of them here.
If a fan is not spinning, it needs replacement.
Once the fans are checked out, and corrected, then the next step is to address why Win XP is complaining.