how can I fix my USB ports?

All 4 USB ports on my laptop have stopped working. The devices ( printer, webcam, external hard drive, mouse) are not recognised, but power is reaching them.
Recently my USB mouse has intermittently failed to reboot from 'stand by'and I simply disconnected and reconnected it without first 'safely removing ' it. This worked ok for a few weeks.
I have run through all the steps listed in Microsoft Help and Support under 'USB May Stop Working' :
scan device manager for hardware changes,
restart computer
disable and re-enable the USB controller
disable the selective suspend feature using Microsoft FixIt.
I have learnt that USB ports are disabled if overloaded( ie more than 500 milliamps). This is a possible explanation as I was using a powered 7 port USB hub.
Is it possible to restore USB ports?
System details:
Fujitsu C series Lifebook
Microsoft XP home Edition Version 2002
Service Pack 3

Any suggestions would be most welcome.