Are there any kind of errors in the Device Manager, or even the Event Viewer?
To get further information about any error look in your Event viewer.
Look in the System or Application folder. You can get to the Event Viewer via right click My Computer icon and select Manage.
Any errors logged in the Event Viewer can be expanded by double clicking on the error line.
Take any event error I.D. number and search for it on these sites.
Also check any "Information" line that mentions "savedump" and you should find reference to "recovered from a bug check". This is the Stop Error that caused your problem if it is in fact trying to reboot when it goes black on the screen.
You can also turn off "automatically restart after an error" so it will just halt at the fault and display the full Stop Error and blue screen.
Right-click My Computer, and then click Properties .
On the Advanced tab, click Settings under Startup and Recovery .
Click to clear the Automatically restart check box under System failure , and then click OK . The error message on a blue screen should remain on the screen so you can record the error information.
Have you tried to use Device Manager to delete the USB root hubs that show on your machine now? Reboot and let XP rediscover the ports.
314634 - Windows XP Does Not Detect Your New USB Device
USB device does not function after connecting device to a Windows XP Service Pack 2-based computer or to a Windows XP Tablet PC Edition 2005-based computer
General USB troubleshooting in Windows XP
HOW TO: Disable the Use of USB Storage Devices in Windows XP
AutoPlay intermittently does not detect removable media or digital cameras
In the BIOS settings for your computer, load the 'Fail-Safe' default settings, and then reactivate the most frequently used options such as USB Support.
Try running ChkDsk to check your camera/drive for errors. Right-click your Camera/Drive icon/ Properties/ Tools/ Error Checking. Select both boxes.
Run the System File Checker program from the Run Box by typing.....Sfc /Scannow in it and have your XP CD handy.
HOW TO: Verify Unsigned Device Drivers in Windows XP
Data Recovery.
Recover Data From Erased Memory Sticks.
Thumb drives