Yay Minnesotan, but anyways, I've read some negative reviews (and a lot of positive ones) about the sound card you have boughten (One stated that if you have a problem with it it may be the way you installed the card). What kind of graphics/sound card are already built into your computer?
Also humor me and take a look at your updates which can be found in (control panel/system and maintance/windows update) and then click on view update history, and see if anything matches up with the time period the problem started.
If you could provide more system specs. that would be helpful.
Take a look at this website, and see if this gets you headed in the right direction
Windows Vista Help: Tips for fixing common sound problems