The only difference is the licensing. With the OEM version is technically tied to the motherboard it's installed on. If you change your motherboard, you're supposed to buy a new license. (OEM stands for Original Equipment Manufacterer & it's technically designed to be loaded on pre-built systems and support is from the vendor - not Microsoft, but I think most people can get by without ever needing to call MS support). The Retail license can be tranferred to another machine, provided it's deleted from the original.
Go with the OEM version. If you notice on the lower left of the product screen on newegg, there is a link for an Upgrade Redemption Form. In short, you may be able to receive a free copy of Vista when it's released in January. (I use the word "may" since there is some confusion right now - Some are saying that you get a free upgrade with an OEM version, while others are stating that it will only be honored if you buy a prebuilt system with Windows preinstalled - so I would ask newegg to be sure).
Either way, the OEM is cheaper - unless you're constantly changing motherboards.
Edit: A final note: The OEM usually has the CD Key on a sticker on the back of the wrapper - be careful not to throw it away! (Believe me, this happens now and then).
Hmm, ok. I might just get Retail just for the heck of it, though. Just incase something happens, or if I upgrade again.
Also, as far as what comes on Windows (such as all the software that is pre-installed), are they both the same? The whole reason why I'm buying a new copy of Windows is because every time I use my HP cd, there is tons and tons of bloatware on it; at least 200mb+. Besides, I'm practically getting a whole new computer from all the parts I'm getting; it'd be stupid to keep the HP stuff for a computer that wasn't even by HP. If you want to see the wishlist, here's the link: http://secure.newegg.com/NewVersion/wishlist/PublicWish...
As far as what comes on the cd - they are identical. Any MS bloatware you don't want to install (MSN Messenger, etc.), you can use the "Custom Setup" option and deselect them.
Going with the retail version is, of course, your choice. Just consider if you're going to be upgrading to Vista before you would upgrade your mobo, then it would be better to get the OEM XP, then the Retail upgrade for Vista. But again, it's your decision & money.
Your system looks pretty nice, I don't think you can go wrong with a DFI motherboard/Opteron combo on the AMD front. The only weak spot is your graphics card. If you're a gamer, you might want to get a card that supports SM 3.0. (Unless you're using the X850 as a "placeholder" until DX10 cards arrive at an affordable price - then the X850 is a good idea).
You're right about the graphics card; it's just a placeholder until ATi comes out with their dx10 cards.
As far as Vista goes, I'm not worried about it at all. The Release Candidate 2 will do me for now; there aren't enough games out yet for me to make a rush on it. And chances are, if XP had a ton of bugs and security threats and the like, then Vista will too. Also, what it seems like is that this "Upgrade Coupon" basically screws you out of XP, deletes it, and installs Vista, am I correct? I'd rather dual boot my computer with XP AND Vista. Makes sense, too. :wink: