Well, thanks for the reply, guys. Sorry for my bad attitude at the begining of the thread. But, it is really not a pleasant experience to return 3 hard drives in 3 weeks and been looked at suspiciously by the BestBuy employees...
From the posts, I can see WD do make good hard drives. I guess it must be my bad luck. Fortunately, the current two drives works fine, I will see how long they last.
To answer billyjak's question, I did update my motherboard BIOS. If there is any problem, it must be the overclocking. I have two computers, this one with WD HDs has P4 1.6A@2.4G 1.725V, FSB 150, Asus P4B266 motherboard BIOS 1005. Personally, I do not think the high FSB killed the harddrives.
To answer Workin's question, I bought the 80GB hard drive from BB since at the beginning of March, it has a $75 rebate, and you can pricematch it from Bestbuy or through Amex Blue to CircuitCity for 149.99, so total is 199-50(PM)-75(Rebate) = 74, or if you do it double side, you get it with only $24. Similarly, for the 120GB, it had a rebate at the end of March for $100, you can get it for 299-120(PM)-100(Rebate) = 79. I learned it from the Hot Deal forum, if you want the details, do a search with key word "western digital" there.
I guess sometimes if you get a too good deal, it has to have something to compensate. In my case, three returns, hopefully no more.