Hi Pals, when I try to on my computer, it shows :\WINDOWS\WINDOWS32\CONFIG\SYSTEM is missing, so it cannot boot. How can I solve this problem without losing the files that are in the system? Pls I want your kind advice... Thanks

Your PC probably has a virus that has deleted a file or some files. What you can do is find out what the missing files are, copy them off a working XP PC or installation disk. Slave the faulty HDD to another PC and put the missing files in the appropriate folders. This should fix it.

yoddy thanks a lot for your post. I will try it

Buy a copy of Windows XP, Then use it to repair the system it will restore back the file

You have to repair the broken operating system but first backup your files in the system. To do this you need to download a liveCD called SLAX. Its a 216MB file. When you have downloaded the file, burn the iso image to a disk. Hope you know how to burn image files?
Next insert the CD in the PC disk drive and set the computer to boot from the CD. It will ask some questions during the boot phase, any computer literate will be able to answer the questions, well just press enter to proceed if you don't understand. Its a mini operating system that runs directly from the disk, thus requires no installation to use.
When it boots to the desktop, you can have access to your computer's hard disk to backup your files. Its interface is different from windows but don't get confused. When you have successfully copied your files to a Flash drive, then can you perform the repair procedure I will describe next.

Get a Windows XP installation disk, insert it and boot from it, as if you want to format the PC
When is gets to the Install Windows page
DON'T select the repair windows installation on the first page just yet, continue as if you want a fresh copy of windows

Press Enter to Install Windows XP
Press F8 to accept the Licence Agreement

It will detects an existing windows installation, and give the option to repair the existing windows installation, select that option. Its the same thing as upgrade. Your programs and files will remain intact.
It is something I have done several times, so don't be afraid. But since you are new to this, I recommend you use SLAX to back up your files first before repairing the operating system to avoid any "if I had known I would have not ..."
I don't expect any issues anyway
Cheers

yoddy: Your PC probably has a virus that has deleted a file or some files. What you can do is find out what the missing files are, copy them off a working XP PC or installation disk. Slave the faulty HDD to another PC and put the missing files in the appropriate folders. This should fix it.

Thank you for your advice I will try this too

this will help you

http://support.microsoft.com/kb/307545