Hi Jacob,
Try to run Finite Sound Input.vi from Labview example finder and make sure that you can acquire at 24bits signal without error(32bits and 64bits will give you a hardware error?), then you can try to update your soundcard driver. Run the attached .vi to finde the current soundcard driver.
Labview 8.0 does support 24bits and you shouldn't see a drop on the S/N ratio when you go from 16- to 24bits resolution(But don't expect a huge increase either). Can you tell me what kind of signal you are trying to sample, samle rate and how do your measure the S/N ratio?
Regards
-----------------------------------------------------
Dennis Morini
District Sales Manager
National Instruments Denmark
http://www.ni.com/ask