What is the difference between OEM and retail for windows 7?

Mainly, a lack of Microsoft support. That being said, if you know what you are doing, you dont need their help in the first place. All I buy is OEM versions. As far as a key from Ebay, wait til you find some foreigner sold you a dud key and lives in bumfudge Egypt. How you gonna get your money back?

EDIT: If you buy an official Microsoft OEM DISK, there is NO bloatware on it.

EDIT: Another myth! ANYONE can purchase an OEM. They DO NOT have to be in business to sell PCs. I've spoke to Microsoft the first time I bought an OEM for this reason

An OEM version can officially only be sold together with a certain piece of hardware, such as a motherboard for example. The license is bound to the purchased hardware in question. In other words, if you would change your motherboard in the above example, your license would not be valid anymore and you would be required to purchase a new license. A retail license is not bound to any hardware. If you would change your entire computer tomorrow, you can simply reinstall Windows 7 and your license would still be valid. There is no support by Microsoft on OEM versions, only on retail versions. Another difference between the two is that an OEM version is simply a disc only, whereas a retail version is boxed.

OEM versions of Windows 7 differ from retail versions in some important ways:

They are dramatically cheaper than retail versions:

As described in the end of this article, the OEM versions of Windows 7 are dramatically cheaper than comparable retail versions. Note, however, that OEM pricing fluctuates somewhat, so the prices you see online could be a bit different. Shop around for the best prices.

They do not come with any support from Microsoft:

Because PC makers support the products they sell directly, Microsoft doesn’t offer any support for OEM versions of Windows 7. This explains the cost differential, by the way.

You are not really supposed to buy them unless you’re building PCs that you will sell to others:

Technically speaking, OEM versions of Windows 7 are available only to those who intend to build PCs to sell to others. Furthermore, online retailers who sell OEM versions of Windows 7 are supposed to verify that you’re a PC builder and/or sell the products with some kind of hardware. For this reason, you’ll sometimes be asked to purchase a hardware tchotsky like a USB cable when you purchase OEM software.

Most of the other guys here are wrong.

There are two main differences between OEM and Retail.

OEM, once installed, is tied to that specific motherboard on that computer so if you install it on one computer then get a new computer or send your computer in for warranty and they give you a replacement, you would have to call microsoft and explain why you are installing Windows 7 on a new computer and they have to authorize the installation on the new computer.

Retail can be installed on whatever computer you want, whenever you want but it is limited to be installed on one computer a time. So if you had it on your computer but it broke and got a new computer, you could install the retail without having to contact microsoft about it.

The other difference is retail comes with support while OEM does not.

Buy the OEM. It is meant for a new system, but can be used for an upgrade or anything else. I wouldn't trust buying a key on eBay.

the retail doesn't give you a ton of bloatware and it also gives you an physical disk. i guess that OEM version probably is in disk form as well. but most OEM versions that are preloaded don't come with the disk.

dont spend either, iv been using a dl win7 retail with the activation hack, and its been working with updates since release, also the hack removes the need to be activated......