If you Usb outputs are created by a card added on the Pci (could you tell us?), you won't find the driver in W98 nor any update - especially if you have Usb 2.0 outputs - nor the chipset driver. You need drivers supplied by the card's manufacturer.
- A Cdrom delivered together with the card
- The card's manufacturer website
- The chip's manufacturer's website
- Websites specialized for drivers.
If looking on the Web, you'll need to know the name of the card, or better, of the chip.