signal drops out with low volumes

I've had a problem recording with my laptop at low volumes.  For example; a guitar chord that fades out sounds fine until it gets real quiet and then it comes in and goes out and then eventually it just doesn't pick up the sound.  It seems to take too much volume to cause it to record.  Is there a setting I need to change to cause my laptop to be more sensitive?  I'm using a Dell laptop with the basic sound card running Windows XP.  I make sure to choose the line-in option because it's coming through a mini-mixer first.

Any help?

It's not unusual for machines like laptops to have cheap old AC97 chipsets in them that implement a permanent noise gate, so that at a level well above the theoretical noise floor, the actual rather high noise floor caused by the built-in cheap analog front end effectively disappears - often quite abruptly. That's fine for things like internet telephone calls, etc but it doesn't do you any favours at all if you want to record proper audio.

But in the same breath, it has to be said that Dells and their built-in sound have been the subject of many a complaint over the years. In some ways, youre lucky it works at all!

I think that the chances of being able to do anything about the cut-off are not good, I'm afraid. The usual solution is to use an external converter, and not bother with the piss-poor internal sound 'facilities' at all.