I did a bit of a search on the forums and did not find this information so I thought I would post it for others reference.
According to the web site, Fugawi Marine has discontinued the Navionics card reader software for the PC.
However, Navionics has created a webb app that allows viewing, not of
your card, but of
their data which appears to be identical to the card data. It even included the buoys in a local lake.
Here is the link. just zoom out till you see the area you are interested in, center it on the screen, and zoom back in.
http://www.navionics.com/en/webappHope this helps