Sludgy-poo

, what motherboard are you on? And plain Win98, or Win98 SE?
General steps, collated:
0. (might be a bit hazy, long time since I've fiddled with a Win9X system). Go to Control Panel...System...Device Manager. Check if there is a USB Controller somewhere (might be labeled USB-to-PCI, or some such). See if there is a ! or X mark next to it. If the controller is absent, go on...
1. Check BIOS for USB Controller Enable/Disable, and Enable. Also there will be a setting for "Plug and Play OS" --
disable that, i.e. "No".
2. If ports are those two at the back, sandwiched between/around all the ports, they are 99.9% integrated, and you do not need to check cables. If these are the ones near/at the bottom of the ports panel, OR at the front of the case, they might need additional cables that connect to pins on the MB. Check.
3. Win98 *should* (after all, it's M$, you never know!) autodetect Legacy USB controllers (1.1) w/o needing special drivers. It should *theoretically* also detect the newer USB2.0 controllers as legacy ones, though it beats me why one would be running W98 on such a new MB

Get back to us on these, we'll get your USB working...