This is from NEC support site. It's an updated sound4 driver for AzTech AT6800W sound/modem card that should fix the turbovbf.vxd problem in Windows 98.
The following files are found inside the driver download file.
|Readme.rtf||2.7 KB||4 Sep 1998|
|SND4-fix.exe||21.0 KB||5 Sep 1998|
|SND4-fix.exe/SND4.INF||1.8 KB||4 Sep 1998|
|SND4-fix.exe/snd4.bat||848 bytes||4 Sep 1998|