I have a 5 year old desktop (XP PRO sp2) with 6 USB ports in total (4
in back, 2 in front).
The 4 in back are 2.0 but I am not sure of those in front.

I have not had a USB issue until recently when I changed my monitor to
one with 4 built-in USB ports.
I installed the monitor and software according to the directions.
I connected the USB cable to the back of the computer.
However, everytime the cable is connected, I am getting errors such as
'USB device not recognized'.
The device manager also shows unknown devices.
I delete the unknown devices and then try connecting the cable in a
different order such as before/after monitor is powered up, before/
after computer is powered up, etc.
I have also disconnected the power cable to the computer (a suggestion
from a computer help forum).

The USB cable from monitor to computer is now disconnected.
All USB devices that were connected at the time the monitor was
installed function OK (such as keyboard, mouse, printer).
However, a USB stick that I have used many times now displays an error
'USB device not recognized' whenever I connect it.
I have tried updating the USB driver but a message similiar to 'You
are already using the current driver' is displayed.

All suggestions are appreciated.

Thank you in advance.