I have an ASUS P4C800-E Deluxe motherboard running WinXP with a pair of Maxtor SATA HDs in RAID 1 mode. This motherboard has a total of 4 SATA connectors, 2 attached to the Intel ICH5R chipset southbridge, another 2 attached to a Promise RAID controller chip. Assuming you want to use Intel RAID, you need to make sure your HDs are connected to the correct SATA connectors.
In BIOS setup, under "IDE Configuration" within the "Main" screen, the "Onboard IDE Operate Mode" should be set to "Enhanced Mode", "Configure S-ATA as RAID" set to "Yes", "Serial-ATA BOOTROM" set to "Enabled". You can also hit CTRL-I during powerup to enter the Intel RAID Configuration Utility to verify that a RAID Volume has been properly created from your SATA HDs.
The floppy diskette generated by the "F6 Floppy Installation Utility" should have the files iastor.inf, iastor.sys and iastor.cat present.
Also, update your P4C800-E motherboard BIOS to the latest available, if you haven't already done so.
Some Maxtor SATA HDs can be powered by either the old-style 4-pin power connector, or the 15-pin SATA power connector. It should not matter which type of power connector is used, as long as one of them is hooked up properly.