Plug and Play not working

Hello all.. sorry for my english, i'm Italian.
I've a strange problem with my Windows XP. I was installing a Logitech
Webcam. I arrived at the step where the install wizard asked me to
plug the webcam into the usb port. I plugged it into a D-Link powered
Usb Hub. After searching a while for the driver, the system gave me an
error ("there was an error while installing the new hardware"). The
wizard suggested me to start a troubleshooting procedure. I started
it, and after a short period of time it said me something like "you
must connect the webcam directly to your pc". So I unplugged the
webcam from the 7 port hub and i plugged directly to an usb port of my
pc. Nothing happened, the wizard was not able to recognize the webcam.
I noticed that at this point the "Plug & Play" service stopped to
work.
If i go in the "Device Manager", i see only a white window, device
manager is empty.
If i go in "Services", Plug & Play service it's started, but the
"start - stop - restart" button are disabled (greyed). It's seem that
Plug & Play service it's no working anymore. Tried to start Windows in
safe mode, but Plug & Play service Start / Stop / Restart button are
greyed and disabled, even in safe mode.
I looked on the web for a possibile solution, but i didn't found
anything to make my Plug & Play service work again.
What i can do? Windows XP Sp2, pc AMD64 4000+, Motherboard MSI K8N.
The webcam i was trying to install is a Logitech Quickcam Pro 3000.
Thank you in advance for your help.
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