Operating system not found

This is usually a sign that the hard drive is failing or has failed. sometimes it can be caused by the system trying to load a CD or DVD in the Optical drive instead of the hard drive.

your hdd is failing my friend. perform a hdd diagnostics. backup your data.

Exactly what error-message(s) do you get?

It's possible that your disk-drive has "failed". Obviously, Windows cannot be loaded from a "dead" disk-drive.

operating system not loading. start w out usbs occupied. if nothing in usb then start in safe mode.if u cant start in safe mode try w operating system disk in. if that fails test real time clock battery. if that fails find way to reformat hard drive. or get another.if u got the pc this way this is a bad sign

When you get to the BIOS window, do you get a message saying that is going to shut down in some period of time of does it just shut down?

Here is my best guess and solution. I believe you've got a worm virus. If you have nothing that you want on this hard drive, and you've got a full install Windows XP disk, I'd do a full install with a complete format, not a quick format, FAT32, if you can, NTFS, if you can't and reinstall Windows XP.

When you power up the computer press F1 ore F2 or "del" key toenter in bios then check your hardisk is detected or not.
If not then if you have desktop open cpu cabinet then reconnect power cable and ide or sata cable to harddisk also check your harddisk is set to master.

1. Restart your computer, hit F8 before windows loading screen to go into the safe mode menu.
2. Select Safe mode (not with networking, and not with command prompt)
3. Once your in windows, goto START>RUN> type “regedit” (without the qoutation marks) and hit ENTER.
4. Goto EDIT, select FIND
5. Search for wgatray.exe, delete any reference found, (after it finds it the initial first time, just hit F3 to continue the search. Continue to delete anything it stops on.
6. Scroll all the way back up inthe registry editor, and select My Computer (one click. not two) and start a new FIND, this time were looking for Wgalogon, again, delete any references found.
7. Lastly, again, click on My computer, and start a new FIND, searching for LegitCheckControl.dll , again delete any references found.
8. Reboot and your finished, if not, you may have missed a registry entry.

Oops---virus may have destroyed the boot sector on your hard disk. Is there a CD in the optical drive, or a floppy in the floppy drive?? If so, remove before booting. If that's not the issue, you need to reinstall the operating system.

As far as original discs---perhaps you can get replacements from Sony if they still support the laptop?

Sure it can be done

Could be a sign that hard drive is failing or a problem with Windows. Do you hear any strange noises, clicks?

Try re-installing Windows and see if that helps.

Thanks!