As I recall, simply looking at the filenames won't harm anything.
From the Navionics swebsite:
>Can I make a backup copy of my chart?
A: No. Navionics charts are write-protected and are unable to be read if copied onto another chip. Please beware that the attempt of copying a chart could corrupt the original chart file and may cause the card to become useless. For boaters who wish to use two plotters simultaneously, utilizing one chip, please contact the plotter manufacturer directly to inquire about the feasibility of a connection. Pending the result, a second chart purchase may be necessary if you wish to run two units simultaneously. Your dealer may give a better discount with the purchase of two cards.
>When we insert our Navionics MMC chip into our MMC reader or directly into the MMC slot on our PC nothing happens. Our PC then tried to go online to find a program and nothing happened. What's wrong?
A: Please note that Navionics charts are NOT PC compatible in just any card reader and are NOT formatted to be read on a PC (as the files are not PC compatible files). You may corrupt the files on your chart by placing it in a card reader and trying to open it on your PC without the proper software and card reader.
There are card readers and software programs that will read a Navionics chart on a PC.
1. Navionics NavPlanner, http://www.navionics.com/NavPlanner.asp
(a Navionics card reader and software package that will allow you to read your current Navionics charts on a PC) $129 US list
2. Raytech RNS software, http://www.raymarine.com/Default.asp...ion=2&page=710
(you will need a Navionics card reader sold separately) to use with Raymarine products.
3. FUGAWI http://www.fugawi.com/web/
(a software package that allows you to use your PC as a GPS system). You may wish to check your chart in your unit to make sure that you have not corrupted the chart and rendered it useless. Please feel free to contact our Customer Service Department if you find that you cannot open the chart on your unit.
Hope this helps;