USB.

While the motherboard is, in a sense, the "Central HUB" of a computer system, a single part can stop functioning while the rest of it continues to work as normal.

Have you tried uninstalling & re-installing your USB drivers? If it's the front panel USB ports that aren't working, you might also want to check that the connections to the motherboard didn't get jarred loose.

Also, can you tell if the USB ports are getting power? or are they just not functioning at all?

Hope some of this helps!

Is this a laptop or a desktop? Because it is usually easier to service a desktop.

Hi, it's a desktop.......

Well, if worse comes to worse, you can always replace the motherboard in a desktop... If none of the USB ports works, it could be a southbridge problem on the mobo, that's the chip that usually controls the USB.
As subasteve5800 suggested, verify your drivers first, via Control panel> Device Manager. If the ports show up there, it's still OK.

THANK YOU BOTH FOR INFO...........

You could try a USB controller PCI card if there's one handy, or if any friends or family have one that you could borrow.

Would be a lot cheaper and a lot less hassle than replacing the motherboard.

Some PCI cards will have their own USB controller, so even if the motherboard has an issue, the card could very well work.

You can pick up 2 port USB PCI cards (here in the UK anyway, for around £5).

Yes, that was always an option, but I thought he wanted the native ports to function... The cards actually connect their USB via the PCI (or PCI Express, depending on the card type), so the added USB ports will work if the expansion cards work. Ironically, they also go through the southbridge, but that does not mean they're dead too. Adding an expansion card will work, even as an alternative to the native USB ports, when no mobo replacement is desired and no need for the native USB ports. Heck, they might add USB 3.0 support, depending on the card.

Hi, I have just purchased a card from amazon at the cost of £10.99. inclusive postage hope i can fix it it's still cheaper than a mobo, thanks for your help, i will probably throw it out the window but one can only try.

No problem, glad to help.