Windows XP is based on the Windows NT platform rather then the Dos platform of 98.
1. Uninstall the Yamaha driver from Device Manager.
2. Locate all drivers relating to Technics in Device Manager, Right click them and select disable.
3. Restart the computer and follow the instructions in the read me file that came with the Yamaha driver.
4. If this works then you can re-enable the Technics drivers, Restart the computer and then see if it continues to work, if it now stops working then you will need to disable the Technics driver whenever you need to use the Yamaha program. (You could also setup two separate hardware Profiles, 1 for the Technics and 1 for the Yamaha and then choose which you require at start up)
5. If the above fails then you will probably need to uninstall the Technics driver, load in the Yamaha driver, and then re-install the Technics driver.
6. You can also try getting in touch with your local computer help centre, explain to them the problems and they may be able to talk you through various diagnostic procedures.
Hope this helps.

Bill