VHS to DVD no audio?



I own a Dell Dimensions 2400 and purchased an V-Stream X PERT DVD Maker to transfer VHS to DVD.
The 1.2 System Requirement:
One available PCI slot
PentiumIII-700 MMX or above CPU
CD-ROM Drive
16MB VGA card with 800x600 16bits resolution (DirectX 8.1 supported)
AC 97 compatible sound card for audio play
Windows 98SE/ME/2000/XP
I am able to burn the video directly to the DVD, without the need to save to HDD, but I cannot get any sound. What do you think the problem is?