If the computer starts fine but Windows fails to load, restart the computer and just after the Bios finishes loading, keep pressing the F8 key until the Windows Advanced Options menu appears.

The menu can only be navigated with cursor keys, so use the arrow keys on the keyboard to select Last Known Good Configuration.

If Windows starts up properly, remove any programs you installed or undo any changes you made recently.

If it still won't start properly, reboot and go back to the Advanced Options menu again by pressing F8 and choose Safe Mode this time.

In Safe Mode, Windows will automatically skip loading programs and hardware components which in 99% of the cases should make it start. Don't be shocked by the low resolution and how awful it looks.

Windows XP comes with System Restore, which takes a snapshot of your computer from time to time. These restore points are usually created when applications or games are installed or a system driver is updated.

So, if you have installed a program that has made your computer unstable, the best way to recover from it is to use System Restore.

System Restore will not delete your data files such as Word and Excel documents, e-mail messages, browser history and such. However, it will remove the programs that were installed at the time the restore point was created.

HANDY: You can use System Restore to return Windows XP to a previous working state.

Click Start > Programs > Accessories > System Tools and look for System Restore.

Once you start it up you will be given the option to Restore My Computer To An Earlier Time. Click Next and follow the on-screen prompts to select a restore point.

At the end of the process System Restore will automatically reboot the computer to complete the restoration process.

Windows repair

If even that doesn't solve the problem then you have no choice but to roll up your sleeves and be prepared to use arcane commands to fix Windows.

Your last resort is the Windows XP CD which has a very useful tool called Recovery Console.

First boot from the Windows XP CD by inserting it in the optical drive and rebooting the computer. You will see the standard Windows XP setup screen loading - proceed till you come to the Welcome to the Setup menu.

Hit R to start up the Recovery Console and press the corresponding number to select the operating system (usually 1 if you only have a single operating system) you wish to repair.

At this point you will be expected to enter the administrator password.

The partition boot sector and the master boot record are essential for Windows to boot. If they become damaged by virus or configuration changes, Windows won't start up.

Fixing the partition boot sector is easy as the built-in fixboot utility will help you write a new partition boot sector and overwrite the existing one which should solve any damage to this part of the system.

Type "fixboot" and press Enter and wait for the process to complete before you restart the system.

If you suspect the master boot record is also damaged then you can also fix it through another command - Fixmbr.

If you have only one drive, type "Fixmbr\Device\HardDisk0" and this should do the trick.

Reinstall Windows

If all the above methods still doesn't fix Windows XP then you have no choice but to reinstall a fresh copy.

Reinstalling Windows back to the original folder should solve your problem but you will lose some settings and some programs may have to be reinstalled to work properly.

However, all your personal data should remain untouched.

Just insert the Windows CD and repeat the process above to get to the Setup screen. Press Enter to initiate Windows Setup and agree to the licence by pressing F8.

Setup will detect an existing copy of Windows installed on you hard disk. Install a fresh copy of Windows to the same directory by pressing the Escape button.

Bad start

If Windows crashes after you log on, then chances are a program that is automatically starting with the operating system is unstable.

There is a little known shortcut to stop all the programs from starting up. As soon as you type in your username and password, and hit Enter, just hold down the Shift key.

This should prevent programs from starting automatically and hopefully not crash Windows.

Now you have to find out the program that is causing Windows to crash and unfortunately this is going to be through a trial and error method.

The easiest way to check which applications start with Windows is to download Autoruns from Microsoft's Sysinternals site at www.microsoft.com/technet/sysinternals.

To launch Autoruns all you have to do is uncompress the zip file you downloaded and run the executable file Autoruns.exe.

You will see a window with many tabs - click on "Logon." Here you will see a list of programs that auto start with Windows.

To disable any of the programs all you have to do is uncheck the checkbox next to it. Don't worry, if something stops working you can enable the program again and restart the computer.

This story was first published in The Star on Tuesday 29 April 2008.