Did you use a VHS camcorder to record your 'old tapes', if my memory of these particular machines is correct they recorded in mono and the recordings were hissy, it might also have something to do with the speed at which the audio was laid down onto the audio track of said VHS tape at the time of the recording. The quality of your capture device may also play a part in the problem and a S-Video lead wouldn't cure it as it only carries a picture signal (higher quality than composite/RCA) and no audio. Do you have an actual digital camcorder? You might be able to rig it up to act as an analogue to digital convertor. You connect the leads from the VCR to the camcorder and then run a Firewire cable from the camcorder to the computer but you don't say if you have one or not.

__________________
Better than a poke in the eye with a pointy stick any day...