I have already searched on the Western Digital website for a Vista driver for the Caviar SE16 KS 250GB Hard Drive that I have installed on my computer and I cannot find it anywhere listed there. I dont know whether the WD team has been informed about this problem or not but it seems that the drive has become useless to me.
I dont think that hard drives need drivers because I am also having the same model hard drive that you own and it is working flawlessly without any issues under my Windows Vista computer.
Even I need some help in my case. I have got 2 external Western Digital hard drives and on Windows XP I dont have any problems with the same drives. I am able to shut them down with one touch and can also put them in standby mode, etc. But in Windows Vista this drives are working when the USB cable is connected but am not able to control them. If I want to shut them down then I am suppose to disconnect the USB cable first and then only I can proceed further. Is there anyone who can help.
You can try to connect the same drive on some other computer and then go into disk management and then from there try to format the drive. Incase if it is not formatting then you can go to disk management and then right click on it and then choose the option to initialize it and then try to format the drive. Check if the drive is working fine now.