There are a variety of situations where a computer will fail to startup properly. These situations often fall into one of the categories below:
No power on:
This is used to describe a laptop or desktop where the power LED lights do not display and there is no image on the screen. For a laptop, a broken charger connector, failed motherboard, failed power supply or dead battery will prevent startup. Test using a replacement charger and battery.
For a desktop, a failed motherboard or failed internal power supply will prevent power on. Some desktop/tower computers also have a power switch on the back of the computer that must be turned on in addition to the front panel power switch.
For desktop computers and servers connected to a “UPS” (uninterruptible power supply) the UPS unit relies on the internal battery power to start unit, even when there is sufficient utility power from an outlet. When a UPS cannot be turned on, this is an indication the internal batteries are failed and require replacement.
Power on, no video:
This is used to describe a laptop or desktop where the power LED lights indicate that the computer is turned on but nothing displays on the screen. For a laptop, power on without any image on the screen can be caused by a failed CCFL backlight inverter or failed LCD panel.
For a desktop, when no image is present on the screen, the screen may be failed. Also, a loose power cord or monitor cable may prevent an image from displaying. Test by replacing with a known good working monitor.
When a computer is using both the Hibernate and Standby power saving options, it is possible for a computer to first go into standby mode and then hibernate and shutdown. This can result in a blank screen when the computer resumes from Hibernate, and then fails to resume from standby mode, leaving the user with a black screen and no cursor. This can be resolved by forcing a shutdown by holding down the power button for more than 4 seconds and then turning the computer back on.
Power on, scrambled video:
This is commonly seen on laptops with a cracked LCD panel. LCD panel replacement is required. This is rarely seen on desktops but occurs where there is bad video memory or a failing video card.
Power on, Windows XP restarts:
The default behavior in Windows XP is to restart when there is an error that stops Windows from working. The result is that Windows will briefly flash a blue screen with white writing, and then restart the computer. The restarting can be caused by a bad motherboard, overheating CPU, failing RAM memory, hard disk drive error, virus, or corrupt NTFS file system.
Any of these problems will generate a Windows stop code 0x7B, preventing Windows from starting up until the problem is diagnosed and resolved. The automatic restart option can be disabled to allow display the stop error code, which will aid in diagnosing the type of problem.
Power on, Windows Vista/7/8 startup repair:
Windows Vista/7/8 try to perform a startup repair that checks for common problems and tries to fix them. This startup repair can take 5-20 minutes and will restart Windows when finished attempting the repairs. For problems including overheating, failed components, bad RAM, virus and hard disk drive error, the startup repair will not resolve the startup failure and Windows will continually repair and restart until the problem is diagnosed and resolved.