Dress the cables. Many OEMs and most individuals neglect this step, but it's an important one. The typical rats' nest of cables that results when you build a PC can impede air flow, causing sporadic problems due to overheating. One system we saw ran fine for a few minutes and then locked up. As it turned out, a loose wire had fouled the CPU cooling fan, causing the CPU to overheat and crash. If you have them, use cable ties to secure individual wires—like those on power connectors—into neat bundles, and then secure those bundles to the frame. If you don't have cable ties, the little yellow plastic ties that come with garbage bags work about as well. Tape ribbon cables in flat bunches and secure them to the chassis, well away from the processor and fans. We've used everything from masking tape to duct tape with equal success, although the heat inside a PC can make some types of tape gummy and hard to remove. Fold over a quarter inch or so at the end of the tape to provide a pull tab in case you need to remove the tape later.

If you have a tape drive or CD-ROM burner, run a full backup and stick it on the shelf. If your backup software allows you to make an emergency recovery disk, make one now.

If you have diagnostic software that provides a burn-in function, use it. Most hardware failures occur immediately. Those that don't are likely to occur within hours or days. When we're not in any hurry, we generally allow a system to burn in for a week or so before declaring it complete. Even when we are in a hurry, we generally insist on burning in the new system at least overnight. If you have hardware problems, it's better to find out now than later.

Reinstall the cover on the case, and move the system to its permanent new location. Connect the monitor, keyboard, mouse, and any other external peripherals. Connect the power cord and start using the computer.

Enter a recurring to-do in your calendar to remind you to check every 30 to 60 days for updated drivers for the main system components, particularly video and sound. This is particularly important if you've built the system using newly introduced components, or if you're using a relatively new release of your operating system.