Why won't my Windows computer start?
On this page:
Electrical problems
The first step is to make sure the computer is getting power. If you don't see lights and hear sound from the computer case when you try to turn on your computer, then your computer is not getting any power. In this case, check the power cables first. If your system has a 110V/220V switch on the back, make sure it is set firmly in the 110V position. Also, if you use a surge protector, make sure it's turned on and you are receiving power from your wall outlet.
If all of these connections are fine but you still hear and see nothing when you turn on the computer, the power supply may be damaged. In this case, take your system to a repair shop to have it diagnosed and repaired.
Note: Sometimes the cooling fan will spin even though the power supply is broken.
If the computer lights up and beeps, but the monitor remains dark, make sure the monitor is turned on and getting power (check for the power light, usually located near the switch on the monitor face). Make sure the monitor, keyboard, and other peripherals are firmly attached to the CPU.
BIOS (CMOS) problems
If you do see the power lights come on and you can hear the hard disk start to spin, check to see if something appears on the screen. There is a built-in program stored in the computer's BIOS (Basic Input-Output System) that checks all of the hardware when you turn on the computer. This is called the POST, or Power-On Self Test. The BIOS stores information about the hardware in your system in an area of memory that is not erased when you turn your computer off. This non-volatile memory is referred to as the CMOS RAM.
When the BIOS finds something wrong with your computer, it flashes an error message on the screen or makes your computer emit a series of beeps. These beeps are actually diagnostic messages. Different brands of CMOS have different beep patterns; see If my computer beeps and fails to boot, what do the beeps mean?
Depending on the brand of BIOS that your computer has, any diagnostic messages that appear on the screen may be either informative or merely cryptic.
If the BIOS tries to access the hard drive in your system and fails, it will (in most cases) alert you to this fact. If the BIOS can't access your hard drive, that does not necessarily mean that your hard drive has failed or that you've lost everything on it. It's much more common that the BIOS has lost the settings for your hard drive configuration stored in the CMOS RAM. This is because the CMOS RAM is maintained by an internal battery, which has a finite lifespan (usually three to five years). When the battery dies, the CMOS settings are lost, and you have to get a new battery and restore the settings.
The settings in the CMOS RAM for your hard drive (such as the number of heads, cylinders, and sectors per track) depend on the brand and model of the drive. Many hard drive models allow several different configuration settings; however, if you use different settings from those used when the drive was set up initially, the drive will be inaccessible.
In most cases, a BIOS error means that you will either have to investigate your CMOS settings or swap components. Usually, you will need to take the computer to a technician. If the boot failure occurs after you have just installed or moved a video card, power down and push the card firmly into its slot, and then try restarting.
Problems with booting
If your computer gets past the POST stage, the problem is most likely something in the Windows boot process. At this point, it's useful to boot into Safe Mode or to use the Recovery Console (Windows XP) or boot diskettes (earlier versions of Windows).
Booting into Safe Mode for Windows 7, Vista, or XP
If you can boot into Safe mode, you can set it to not load certain drivers, disable startup items, run ScanDisk, and use a number of other diagnostic tools. See In Windows, how can I boot into Safe Mode?
Using System Recovery Options in Windows 7 and Vista
In Windows 7 and Vista, you can use the installation disc to access the System Recovery Options menu. For more, see system recovery options in Windows 7 or Windows Vista.
Using the Recovery Console in Windows XP
If you have Windows XP, you can use the Windows XP installation CD to reach the Recovery Console and access DOS (the command prompt).
Viruses
It may also be that your computer is infected with a virus, in which case UITS recommends reinstalling your operating system. For more, see Why do I have to format and reinstall Windows after my computer is infected with a virus?
For information about Support Center walk-in offices (hours and locations), see UITS Support Center walk-in locations and services.
Last modified on May 03, 2011.
