The SD card is not set up for any particular unit.
The data file that the Humminbird unit's read is called DATA.HWR,
in the MATRIX folder.
HumminbirdPC can't read DATA.HWR directly, but must
convert it first to a GPX file.
If HumminbirdPC can't open/convert the DATA.HWR file, it may be
corrupted. If you double click on the file name (on your SD drive), it
should ask you if you want to convert it to a GPX file.
If all else fails, try exporting the data (from the 898), to a new SD card.
Good Luck.
PS. The 898 model is newer than the 797.
I don't think so, but maybe it's possible, but highly unlikely, that there is some type of format
change with the waypoint files. Greg would know for sure.
Also, make sure you are running the newest version of HumminbirdPC (version 4.3.8 ).
Also, it's possible that the size and speed of the SD card used in the 898 is not compatible with
your older unit. You may have to get a slower/smaller card.