It seems that many people are still getting the 'USB Device not Recognized' problem from time to time. Unfortunately there is no easy fix.
Firstly, it's recommended that you make sure every one of your motherboard drivers are completely up-to-date, but you probably already knew that.
In XP, after a USB port isn't used for a long while the USB driver built into the OS sets the OHCI controller to suspend. When you plug a device back in, it can sometimes fail to 'wake up' properly. This problem was supposedly fixed in SP1 but there is a related registry hack that may still be able to help.
Run regedt32.exe and navigate to; HKEY_LOCAL_Machine\SYSTEM\CurrentControlSet\Services\Usb
Create the Usb
key if it doesn't already exist. Under this key, create a new DWORD value called DisableSelectiveSuspend
and give it a value of 1. Then restart the PC.
A long shot perhaps, but I recall having similar problems with a USB hub built into my Microsoft keyboard and adding this key seemed to solve it. It wouldn't hurt in trying
Alternatively, removing all entries relating to USB in Device Manager and all associated USB drivers will force XP into refreshing the USB driver stack.
Begin by unplugging all USB devices, then use Add/Remove Programs in Control Panel to uninstall any USB driver software. Next, boot up into safe mode and go to Device Manager. Once in device manager make sure 'Show hidden devices' is checked under the View menu. Uninstall all device entries in this order;
1. USB peripheral devices
2. HID and/or Composite USB (Human Interface Devices)
You're using PS/2 input devices so you may not have this entry.
3. USB Root Hub(s)
4. USB Host Controller(s) (Universal or Enhanced Host Controllers)
Then boot back into Windows (not safe mode) and it should populate the Root Hubs & Host controllers again. Proceed to plug your USB devices back in, starting with your powered hub. Be aware that most USB printers and scanners need to have their drivers installed first before you plug them in.
Hopefully some of this may be of help, let us know how you get on.