Just noticed this forum and have a few comments.
First of all, it seems that not all motherboards supply power via the serial cable. That was the case with my Intel D845PEBT2 which is a 2.4Gh P4 system. Although that may be obvious, if your drive is not recognized it may not even be spinning. In that case use the legacy power connector.
Regarding Drivers, I just downloaded the latest one, 14 June, 2004 from Microsoft. For the Silicon Image Sil 3112 SATALink Controller built into the mother board the driver version is V184.108.40.206.
Regarding sockets, if you are not using RAID, be sure to set that up in the BIOS and use just the primary SATA socket.
Having said all that, I'm stlll not running with my 250 Gb WD Caviar drive. It is recognized by the device manager which also gives me the size, model number, and serial number, but it is not recognized by the WD diagnostics. In addition, I have a problem now which came with some windows update. The system will not connect to the Logical Disk Manager Service.
That's the next hurdle and it seems to be a Microsoft XP Pro Sp1 problem.