Whatever else may be wrong with your PC, you know it's pretty serious when Windows won't even start.

This article appears in the May 07 issue of PC Advisor, available now in all good newsagents.

Perhaps the most dreaded PC problem of all is switching on a PC, only for nothing to happen. It's clear there's a major problem, but since there's little to go on, it can be a difficult issue to troubleshoot. Many people give up on their ageing PC or send it straight to their local PC repair shop once they start having trouble booting Windows. This may result in a duly fixed PC, but it's often an expensive option and one you shouldn't need to entertain if you follow our fix-it guide.

If you don't hear anything, such as the whirr of a fan, when you fire up the PC, the PSU (power supply unit) may have failed or come unplugged from the motherboard. If fans start up but there are no beeps, the problem could be with the motherboard. A series of beeps indicates hardware faults such as memory, video adaptor or CPU (central processing unit) problems. These will vary depending on your Bios (basic input output system). Finally, a message such as 'Disk Boot Error' or 'Non-System Disk' indicates a hard drive error. Some of these can be rectified by the operating system; others may be caused by a hardware fault.

Often, the problem has nothing to do with hardware. If it's a software problem there's every chance you can get your PC started again.

Windows usually fails to start when a program or device has been installed that conflicts with another. A number of simple workarounds can be used to tackle such problems. For example, if the operating system begins to load but doesn't get to the desktop you may be able to rectify the fault by loading Windows in Safe Mode.

Advanced troubleshooting

More significant difficulties can arise when data on the hard drive has been corrupted. In this case Windows won't load even in Safe Mode. For Windows XP and later versions, Microsoft provides a Recovery Console that can be accessed from a bootable Windows disc. The Console provides a command prompt and access to tools to repair your system.

Corrupt or faulty Boot.ini files, partition boot sectors or master boot records are common reasons why an operating system won't load. Windows 2000 and subsequent releases rely on a Boot.ini file to tell the Ntldr (NT Loader) program where Windows resides and which options to load. If
this is damaged, the OS won't boot correctly. The partition boot sector contains information about the file system as well as crucial information to load Windows, while the MBR (master boot record) sits on the first sector of the disk and tells the OS where to find the bootable partition. If either is corrupt Windows may fail to start.

Good housekeeping helps. Prepare for the worst by keeping an emergency boot disk. If your hard drive's boot sector or Windows' basic boot files have been corrupted, this disk will circumvent the problem and boot your PC into Windows. If you don't have an emergency boot disk, you may be able to use one created on another PC running Windows XP or Windows 2000. There's no guarantee it will boot your machine, though.