In planning to build a computer, the majority of a persons thinking centers on the CPU, motherboard, and hard drive. What case to use is of secondary concern, with the decision based often on personal taste rather than technical reasons.

Some builders may want to re-use an old case.

The logic of it seems sound. Perhaps you have an old computer, nothing of which is salvagable but the case. Or, maybe a friend has gutted his old system, scavenging parts to make a new computer. Re-using a case can shave dollars off the cost of your new system, and make use of an item that might otherwise be trashed.

In the light of reality, however, using that old case makes economic sense only if it comes with a sufficent power supply to fill your needs. Many older cases were sold with 230 or 250 watt units. These are completely inadequate for todays needs.

The most basic internet and homework sort of computer requires 300 watts. If you have ambitions of anything beyond web browsing and word processing, then start thinking higher. For some pursuits much higher. Top level gaming and heavy duty video work may require 500 watts.

If you still want to use that old case, theres a lot you can do to upgrade it. The most obvious move is to install a stronger power supply. Since they usually mount with only 4 to 6 screws, this is an easy operation. Just lately, Ive noticed some 400 watt units being sold at bargain prices, so this can be done without busting your budget.

If you need firewire and USB ports in the cases front, they can be installed in one of the 3.5 inch bays. Low cost kits, that come with cables, can get the job done. You can hook up cameras, flash memory, and other good stuff without fiddling about in the back of the case.

Does the case need a new fan port cutout made? Now is the time to do it, while the case is empty. My prefered method is to saw out a small rectangle, and cover the hole with steel mesh. I use the screws that hold the fan to keep the steel clamped in place.

In the cases previous use, PCI cards probably were installed, and now youre left with one or more holes than need to be filled. If you can mount your cards there, do so, or get replacement caps to cover them. Leaving the holes open can let a lot of dust in, and change the airflow patterns, reducing cooling efficency.