From what you say I can only assume it is the software supplied with the 
camera for downloading the pictures that is not working correctly for some 
reason.
I assume you are using this software and not explorer in xp. I see you are 
not running SP2, this may help, but you say other devices work at USB 2.0 
speeds.

Is it possible to try the camera on another PC to see if the same issue 
exists. Have you tried another USB lead between the pc and camera.

I personally never connect any of my digital cameras to the pc or load any 
supplied camera software. I always use a card reader which
works fine at USB 2.0 speeds (providing it is a USB 2.0 reader). Using more 
expensive faster cards helps also, but it can take a few mins to download 
2GB.

One final thought, I see from the computer specs that it is a few years 
old - you are certain its USB ports are 2.0 and not 1.1, and are fully 
complient to the USB 2.0 specifications. If
not you could buy a PCI card with 4 USB 2.0 ports for about