Quickly check jumper SATA_EN1 and make sure the stint is still on pins 1 & 2. Just to get that out of the way:p
The Manual also says that "Hot plug support for S/ATA drive and connections are not available on this board". For starters, this tells me that the S/ATA may not be native, meaning it needs a driver. Try to update the driver for the chipset, controller, and I guess for the drive. Then I have to ask if you're plugging and unplugging the controller "hot". And just a curiosity weather you are using a S/ATA power cable on that drive along with the data cable. Juuuuust wondering, that's all
I've also heard bad things happening with WinXP SP2. If you reply that you've downloaded SP2, I'll dig in further to see if this has anything to do with your problem.