You need the drivers for the card to use USB 2.0 with W98SE. Of course, with a Dell machine, who knows why it doesn't work! 
In the BIOS, have you reset the ESCD in the BIOS? Here's a page talking about the ESCD: http://www.dewassoc.com/support/bios/escd.htm
FWIW, I've used a number of USB 2.0 boards with the drivers in W98SE machines successfully, but it's been a while since I have tinkered with W98.
In the BIOS, have you reset the ESCD in the BIOS? Here's a page talking about the ESCD: http://www.dewassoc.com/support/bios/escd.htm
FWIW, I've used a number of USB 2.0 boards with the drivers in W98SE machines successfully, but it's been a while since I have tinkered with W98.