#MSDN (Microsoft Developer Network)

Uniqe copy for each participant and researcher in the development programs of Microsoft Corp.,Not for sale and have its serial
and You can request free technical support from Microsoft

##RTM (Release To Manufacturing)

A copy specially made for computer labs like Dell, Hp, Toshiba labs
and its very Expensive and comes like (OEM) that means
Original Equipment Manufacture

###Retail

Directed users to copy sold in ordinary shops in a box with serial
supported with Microsoft