Motherboards that are not one of the industry standard form factors, such as AT/Baby-AT, NLX, or any of the ATX formats, are deemed proprietary or semi-proprietary. LPX, ITX, and mini-ITX systems fall into the semi-proprietary category for example, while other companies have fully proprietary systems that only they manufacture.

Most people purchasing PCs should avoid proprietary designs because they do not allow for a future motherboard, power supply, or case upgrade, which limits future use and serviceability of the system. To me, proprietary systems are disposable PCs, because you can neither upgrade them nor easily repair them.

The problem is that the proprietary parts can come only from the original system manufacturer, and they usually cost much more than nonproprietary parts. Therefore, after your proprietary system goes out of warranty, not only is it not upgradeable, but it is also essentially no longer worth repairing.

If the motherboard or any component on it goes bad, you will be better off purchasing a completely new standard system than paying five times the normal price for a new proprietary motherboard. In addition, a new motherboard in a standard form factor system would be one or more generations newer and faster than the one you would be replacing.

In a proprietary system, the replacement board would not only cost way too much, but it would be the same as the one that failed. Note that you might be able to perform limited upgrades to older systems with proprietary motherboards, in the form of custom (non-OEM) processor replacements with attached voltage regulators, usually called "overdrive" or "turbo" chips.

Unfortunately, these often don't perform up to the standards of a less expensive new processor and motherboard combination. Of course, I usually recommend upgrading the motherboard and processor together—but that is something that can't be done with a proprietary system.

Until the late 1990s, the LPX motherboard design was at the heart of most proprietary systems. These systems were sold primarily in the retail store channel by Compaq, IBM's Aptiva line, HP's Vectra line, and Packard Bell (no longer in business in North America). As such, virtually all their systems have problems inherent with their proprietary designs.

If the motherboard in your current ATX form factor system dies, you can find any number of replacement boards that will bolt directly in—with your choice of processors and clock speeds—at great prices. You can also find replacements for Baby-AT motherboards, but this form factor doesn't support the newest technologies and has not been used in new system designs for several years.

However, if the motherboard dies in a proprietary form factor system, you'll pay for a replacement available only from the original manufacturer, and you have little or no opportunity to select a board with a faster or better processor than the one that failed.

In other words, upgrading or repairing one of these systems via a motherboard replacement is difficult and usually not cost-effective. Systems sold by the leading mail-order suppliers, such as Gateway, Micron, Dell, and others, are available in industry-standard form factors such as ATX, micro-ATX, flex-ATX, and NLX.

This allows for easy upgrading and system expansion in the future. These standard factors allow you to replace your own motherboards, power supplies, and other components easily and select components from any number of suppliers other than where you originally bought the system.