A friend of mine had the 1TB Samsung drive in his new desktop computer die after 6 weeks so his computer supplier replaced it with a WD 1TB Green drive. He is still running Windows XP and it looks like there is some additional setup required to use these new WD drives under Windows XP.
His new desktop is a dual core Intel 3Ghz machine and it should have run like a scolded cat but it crawled along like an old 386 and the disk IO light was almost permanently on. The machine would appear to hang for periods for up to 30 seconds.
A bit of research revealed a suggestion that for older operating systems like Windows XP you need to run a utility called WD Align to address the IO issues. He ran that utility, its a non destructive utility, and IO improved markedly.
I haven’t finished researching everything yet but appears that these new WD 1TB drives are what are called "advanced format drives" and use 4K sectors instead of the older 512b format. Don’t fully understand why this causes such bad IO and why the WD Align utility fixes it but there is a good article here
It appears that newer Operating Systems such as Window 7 cater for these newer advanced format drives.