Usb Ports Are Not Working(recognized) In Dell Latitude D600 Laptop

Hello friends ,

I am new comer in this forum. I have a problem in my Dell Latitude D600 laptop.The laptop has 2 USB ports and they were working fine.I used pendrives and usb modem at this ports. But one day suddenly the two usb ports were not working.

To resolve the problem I did some experiments, they are below....

1. Properly cleaned the USB ports and motherboard.
2. Reinstalled operating system. ( Installed Windows XP and later I installed Windows 7)
3. Also installed driver for USB 2.0.
4. Installed motherboard driver properly. Also downloaded updated driver from dell website and installed.
5. Bios settings set to default and usb options set to on position.
6. Also visited this website for details...
Documentation

But I am failed. Friends, have you any solution for this kind of problem ? If yes, please help me. You can mail me. My email ids are : [email protected] and [email protected] . Thanks in advance. Bye.....