OEM stands for Original Equipment Manufacturer. Oem software is generally only sold by hardware manufacturers who include the OEM software as part of the total product. For example, when you purchase a new computer and it comes with Windows, it is the OEM version of Windows. Software wise there is no difference between the OEM copy and one you would buy from a store, but the manufacturers buy it in such bulk that they get huge discounts. On the other hand, there is a big difference with OEM software and the other versions when it comes to the support you can receive for the product. If you own an OEM version of a piece of software then you must get support directly from the equipment manufacturer instead of the creator of the software. That means if you have an oem version of Windows XP that you received when you bought your computer, support for Windows XP can only be received from the manufacturer of the computer and not directly from Microsoft.

Academic and Not For Profit versions of software are software that is priced for a specific type of institution. Manufacturers generally sell their products at a steep discount if the buyer can be considered a educational institution or a non for profit institution.

Upgrade Versions is a way software companies have you continue to use their software or to switch to their software. These upgrade versions are usually the same as their Full Version counterparts, yet are at a significant discount. When they the Upgrades are installed on your computer, if they do not detect a piece of software that they feel is from a previous version or similar application, the upgrade will not work and it will direct you to buy the Full version. The upgrade is always cheaper than the Full Version, sometimes up to 50% cheaper.

Full Version software is exactly as you would think it would be. It contains the full software and can be installed on your computer regardless of whether or not you had a previous version or similar application installed. These versions are always the most expensive, and as there is generally always a way to get away with using an upgrade, you should never purchase a Full version of the software unless it is absolutely necessary.

Hope this clears up the different versions of software that you can find available.