I have the ASUS P4C800-E MB Deluxe and a WDC 250 GB SATA Disk Drive.
I am running Windows XP Pro SP1 with the ASUS Motherboard's BIOS Revision 7.
I want to achieve the fastest performance possible so I connected the WDC 250 GB SATA Disk Drive to the ASUS Motherboard's onboard Serial ATA ICH5R Connector to obtain the 150 MB Data Transfer Rate.
The onboard Serial ATA Interface is faster with the 150 MB Data Transfer Rate then the onboard Promise PDC20376/78 RAID Controller that only supports the 133 MB Data Transfer Rate.
I plan for now to have only one SATA 250 GB Disk Drive in the Computer.
In the IDE Configuration BIOS Setup Screen I have the following settings.
Onboard IDE Operate Mode - [Enhanced Mode]
Enhanced Mode SUpport on - [S-ATA]
Configure S-ATA as Raid - [No]
Serial ATA Bootrom - Disabled (This Field Only Appears When The Item Configure SATA as RAID is set to Yes)
IDE Detect Time Out (Sec) - 
Is there any performance or reliability advantage in setting the one WDC SATA Disk Drive in a RAID 0 Configuration using the RAID Feature of the Intel ICH5R Chipset, then leave it in the non-Raid Configuration that it is now?
Another System Problem that I have is the Found New Hardware Wizard the "WinXP Promise SATA-378 IDE Controller" keeps popping up.
When I install the Device Driver Software, it tries to load the "Ulsata.Sys" File from the "ASUS" System Software Support CD-ROM Disk from the following Path "\Drivers\Promise\378ata\winxp".
When it is finished I receive the System Error Message
"Cannot Start This Hardware"
"There was a problem installing this hardware:"
"WinXP Promise SATA378 IDE Controller"
"This device cannot start. (Code 10)
I tried this procedure many times and the "WinXP Promise SATA-387 IDE Controller" will still not load properly.
Any ideas why the Device Driver Software for the "WinXp Promise SATA-387 IDE Controller" will not load?
Since I am not using it should I just disable the Promise Disk Controller in the Motherboard BIOS, or try to obtain the Software Device Drivers from somewhere else?
I have the same board. You cannot set sata as raid because you only have one hard drive. Redundant Array of Inexpensive Disks (RAID)- you need at least two hardrives to have raid. I use the ich5r with two 120 seagate sata hard drives. I use raid level 0 (striping) for performance. I could also do raid 1 (mirror) which makes an exact duplicate of your hard drive (used for backing up important data). If you only have one hard drive your settings are correct. About your other issue make sure you have the promise controller disabled in the bios. I always disable it before I even install windows. If you look at asus's website you'll see many updates for the promise controller so maybe there are a few bugs with it. Good luck.