Have not seen that make before but the chipset is one that's used by Abit and I've not had a problem (yet), has the WD drive got any jumpers on it to allow you to switch between SATA I & II? if so forcing SATA I mode might help as the host card is SATA I if that's not possible/dos'nt cure it I would try the card & HDD on another machine if that's possible failing that try and RMA the card first (cheaper option) second would be to find a machine with onboard SATA ports and plug the WD HDD into one to see if the problem follows the drive. Not a quickfire solution I know but I can't think of anything else right now sorry.
Checked your irqs ? You have installed a pci card. It will need a irq, normally a dedicated irq although some cards can share most cannot.
With so much stuff on MBs these days requiring an irq this does happen quite a bit.
Try checking your irqs to see if there is conclict, this is basic shit anyone installing cards should know already.
Go to device manager, choose view resources by type and make sure nothing else is using that irq.
If something is you can try another pci slot or you can try changing the irq settings in your bios. Each mb is different there so youll have to figure it out.
When I got my athlon slot-a 500mhz wayyy back when they first came out I was sharing my directory with my mp3s on my local network.
If I was listening to music on my sb live! and my brother tried to get a file from me my computer would reboot since there was an irq conflict.
Needless to say I quickly fixed that.