Do a final check of the system, making sure that all cables are connected properly and that you haven't left any tools in the patient. Do not underestimate the importance of this final check. We have seen newly built systems shorted out and destroyed because a tool, screw, slot cover, or other conductive part was left where it shouldn't be. In fact, we always pick up the system and shake it gently to make sure no extraneous parts have been overlooked.

Connect the monitor, keyboard, and mouse to the appropriate ports on the computer. Connect the power cord to the PC power supply and then plug it into a wall receptacle. Turn on the monitor.

Turn on the PC. If all is well, the hard disk spins up, the BIOS screen appears on the monitor within a few seconds, and the system beeps to indicate a normal boot. If the system appears dead or beeps repeatedly, immediately disconnect the power and verify all cable connections and configuration jumpers. The most common problem is a floppy drive cable connected backward—which causes the floppy drive indicator to light and stay lit as soon as power is applied—or an IDE cable connected backward, which may cause the system to appear completely dead. In either case, check the cables, correct any problems you find, and reapply power. Repeat this process until the system boots normally.

Some motherboards require running BIOS Setup immediately to allow the system to self-configure. Doing that never hurts, so when the system prompts you to "Press <key-name> to run Setup" (or words to that effect), press the indicated key to run BIOS Setup. Don't make any changes to BIOS settings now. Simply save the default settings, exit, and allow the system to restart.

Check the BIOS boot screens to make sure that all installed components are recognized properly. In particular, the initial memory check should display the correct amount of memory, and the screen(s) that list installed devices should show all installed ports and IDE devices. IDE/ATAPI devices should be listed correctly by name or model number. Devices that require drivers are not recognized at this point, which is normal. On fast systems, screens often flash by too quickly to read. Press the Pause key to interrupt the boot process long enough to read each screen. To continue, press the spacebar.

After you verify that all devices are recognized, restart the system and run BIOS Setup again. With most systems, you need change only the time and date, and perhaps set the processor speed. Default values work perfectly well for other BIOS settings. Use the motherboard manual to determine which, if any, settings need to be changed. If you plan to delve deep into the BIOS settings to tune your PC for optimum performance, the motherboard manual may be of little use. Most provide only abbreviated descriptions of the most commonly changed BIOS settings. For detailed information about obscure settings, visit the web site of the BIOS manufacturer and download the full documentation for your BIOS version. Even with that information, however, you may find many BIOS options difficult to understand. We have found The BIOS Companion by Phil Croucher very helpful in deciphering obscure BIOS settings. You can order it directly from the author's web site at http://www.electrocution.com/biosc.htm.

If you have devices (such as a network card or SCSI host adapter) that have their own ROM-based setup programs, run those programs per the manufacturers' instructions.

When you complete BIOS Setup, save the changes and exit. Power the system down. Some motherboards, notably Intel models, have a configuration jumper that is set to one position for Configure and another position for Normal Operation. If your motherboard has such a jumper, move it to the position that sets the system for normal operation.