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The cheaper ones are OEM. They come in a vacuum sealed plastic bag with no box (those are the ones I buy). The more expensive ones are Retail = Box with brochure.
 
Since you are shopping, consider this one: http://www.newegg.com/Product/Product.asp?Item=N82E16822136073

I have 2 of them and they are SO silent!

I also have a RAIDED pair of raptorsX 10K that I started using as boot disks but the repetitive screech-cruck-grack-grack wasn't worth the extra speed for my daily tasks. I use them now as CS3 scratch disk. I'm not such a power user to really take advantage of the speed so if I would do it over I would have bought 2 more of those 500s above and saved almost $200

Cheers
 
Since you are shopping, consider this one: http://www.newegg.com/Product/Product.asp?Item=N82E16822136073

I have 2 of them and they are SO silent!

I also have a RAIDED pair of raptorsX 10K that I started using as boot disks but the repetitive screech-cruck-grack-grack wasn't worth the extra speed for my daily tasks. I use them now as CS3 scratch disk. I'm not such a power user to really take advantage of the speed so if I would do it over I would have bought 2 more of those 500s above and saved almost $200

Cheers

I just bought two of those too. WD has worked well for me for years.

As to Raptors and RAID 0, might be time to rethink the concept of Raptor being king of the hill. You can buy two of those WD5000AAKS 500 gigs and put them in RAID 0. You will spend a little less for that terabyte of storage than you would for a single 150 gig Raptor, and the RAID will be faster in almost every category.
 
And the nicest thing about the larger WDs is they're even faster when they're less full. A half-full 500GB drive is going to be faster than a next-speed-up 250GB drive that is full.
 
And the nicest thing about the larger WDs is they're even faster when they're less full. A half-full 500GB drive is going to be faster than a next-speed-up 250GB drive that is full.

That's common with all hard drives--they're slower as they get more full.
 
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