|See response 2 regarding inadequate for USB 2.0, broken or damaged wiring to the front ports. |
Make sure all the USB controllers are turned on in your bios Setup pages.
"Also for some days the device manger reported unknown device under the USB category even there all the ports were physically empty!"
That unknown device is probably not about any device you plugged in or an imaginary device - it's probably about the USB 2.0 controller(s).
If your XP CD does not have SP1 or SP2 updates built in (it's printed on the CD if it does) XP cannot recognize USB 2.0 controllers (and hard drive sizes larger than 128gb as seen in Windows) until you install at least SP1 updates. When those SP1 or SP2 updates haven't been installed yet, you will have an unknown USB device in Device Manager (for the USB 2.0 controller but it doesn't know what it is at that point), and the USB controller's USB 1.1 support will work fine, but there is no USB 2.0 support.
Also, even if you do have SP1 or SP2 updates included on your XP CD, whenever you install Windows from scratch, after Setup is finished you must load the drivers for the mboard, particularly the main chipset drivers, to makev sure that Windows has all the proper drivers for and information about your mboard - otherwise, aongst other things, Windows may not detect the USB 2.0 controllers are there.
Also take a look at the inside of the port on your front USB ports on the case front - if the plastic tab in the port is broken or missing, or it if any contacts are bent, whatever you plug in may not touch the contacts inside the port properly, and in that situation no USB device will be recognized in the affected port.