OEM stands for Original Equipment Manufacturer.
In the MS World, should only be sold by MS OEM Resellers.
OEM Software can only be sold with a new PC or with a motherboard + cpu + ram + hdd combination. (as defined by M$)
OEM Software from Microsoft does not feature a box, useful manuals (altho, is retail any more useful?) - usually only a EULA and a Installation Guide, CD-ROM and license sticker. Basically, no frills. Since Win2K, if u buy the boxes of 3, you get extra software to customise the setup and to stick your ugly corporate logo all over the Systems Properties dialog window.
Retail is a boxed product - can be bought by anyone, without the need for purchasing a brand new PC and should come with better documentations and frills.
I am quite sure, in the MS World, there is no difference over warranty issues.
Hope this helps,
Samuar
