SY-P4RC350 USB 2.0 problems

Finishing up my first ever MB upgrade. Everything works except USB2.0.
Getting "Unknown Device" & "drivers not installed". Looks like driver
problem.

MB is SY-P4RC350. OS is WinXP SP2. Started with Win98SE. USB2.0 worked
until I screwed something up (don't know what). Formatted HD, reloaded
Win98SE, then upgraded to WinXP SP2. USB1.1 device works great. USB2.0
doesn't.

Soyo web-site says VIA chipsets (mine has VIA VT6122) running XP must
have SP1 loaded to get the necessary drivers. Those should be in SP2,
right?

Any suggestions? Thanks.