KT600-A v1.x maximum CPU and HDD supported information as below,
HDD:400G
CPU: AMD Duron 200Mhz FSB CPU - 950 AMD Duron 266Mhz FSB CPU - 1800
           AMD Morgan 200Mhz FSB CPU - 1.4G 
           AMD Athlon 200Mhz FSB CPU - 1.4G AMD Athlon 266Mhz FSB CPU - 1.4G 
           AMD Palomino 266Mhz FSB CPU - 2.1G 
           AMD Athlon XP (0.13u) 266Mhz FSB CPU - 2600+ AMD Athlon XP (0.13u) 333Mhz FSB CPU - 3000+
           AMD Athlon XP (0.13u) 400Mhz FSB CPU - 3200+ 
           AMD Sempron 333Mhz FSB CPU - 3000+

Please follow the steps below to install Win XP.

1. Boot system from OS installation CD in the CD/DVD-ROM. 
2. Make sure your BIOS has updated to VT6420 during POST. 
3. Press "F6" when OS setup starts running. 
4. Insert floppy disk. 
5. Choose the OS device driver to load SATA driver.
6. Install OS.
7. Run setup.exe to install MB drivers after OS is installed.

The KT600-A did not support the hard disk LED for SATA HDD.

No, the KT600-A does not support S3 function.

To boot from PATA device, please set the "First Boot Device" to [HDD-0].
For SATA boot, please change the "First Boot Device" to [SCSI].

The latest  AWARD Flash utility for KT600-A is v8.32 as attached file.

Please set "CPU FSB clock" from 100MHz to 166MHz in BIOS to get the correct processor frequency.

1. Please update BIOS to v1.2C attached and flash the BIOS under DOS mode.
2. After flash finished, please access BIOS Setup to enable "Onchip SATA Device" of  "Integrated Peripherals".
3. Then the SATA HDD should be detected on POST.

Please set the jumper to 166MHz(JP8 2-3 JP9 2-3) on the MB.

No, the KT600-A 1.0 doesn't provide "CPU voltage adjustment" because it's possible to cause CPU demage.

KT600-A doesn't support K/B power on function, please refer to the user manual on page86 for the detail.

It's the limitation. You could not inser the front MIC or Headphone jack if you want to line out the speaker from the back I/O panel.