Car dealerships have nothing on computer sellers. It pays to be a shrewd computer shopper these days, because the computer you think you paid for may not actually be what you take out of the box. And the differences are pretty subtle.

Computer prices are rather like New England weather; if you don't like them, wait a minute--they're bound to change. The fast pace of progress in the computer industry means that newer, faster models are always on the immediate horizon. While this is good for buyers, it also provides an opportunity for manufacturers to be a little sneaky. Recently, there has been a increasingly common trend by manufacturers to obscure the differences between older and newer models. This helps the manufacturer unload their inventory of older machines without having to offer drastic discounts. Unfortunately, unsuspecting buyers may wind up paying a premium price for a model that is really ready for pasture.

One common example are desktop and notebook computers using Celeron processors. The first 300MHz Celeron chip was notoriously slow, forcing Intel to quickly come out with a newer and faster 300 MHz Celeron chip, designated the 300A. However, many systems based around the older chip were never taken off the shelves, so consumers not on the lookout for "non-A" 300 MHz Celerons often could (and can) get stuck with a much slower processor and never know it.

Another situation concerns minor updates and changes made to computers during a production run. Apple iMacs come with a round mouse that requires a close look to tell which way is up. Recent models have added a small divot on the front of the mouse to help users feel which way to point the mouse. A minor detail to be sure, but the new design may be enough to eliminate the need to shell out for a third-party pointing device, as some users have done. Yet it can be nearly impossible to tell which models offer the improved mouse.

A third way you can lose out is to get stuck with an older operating system or application versions. We recently saw an online vendor's product search return two versions of the Fujitsu Lifebook E340, both notebooks with identical product specifications--except for price. A closer look revealed that the more expensive model actually came with Windows 95 installed. Its (inexplicably) cheaper twin came with the newer Windows 98. The only difference was a "95" or a "98" at the tail-end of a 24-digit ID code.

To avoid these kinds of mistakes, make sure to closely examine a product's packaging. Often, a close look at the ID code a manufacturer uses to identify the product will clue you in. The only difference might be one digit in the manufacturer ID, or an "A" or a "B" at the end of the product's name. If you see models with similar, but not identical, ID numbers, ask about the difference. If the vendor you're buying from doesn't know, make sure to check out the manufacturer's website for product specifications, or consider calling its customer support line. It may save you from paying today's price for yesterday's technology.

Quick tips

Read up before buying. Online computer magazines are often in te know about unadvertised upgrades or subtle revisions make to computer products after their initial release. Monitor the web after you buy. Manufacturers sometimes support their products by posting upgrades or software patches on their site.