Garmin Data Card w/ GSD 21

I got a Marine Software Update Data Card in the box with my new depth
sounder. After I use this card to do the update, can I erase it and use
it for uploads from the CD's?

I have search the web for a place to ask my Data card question. Not off
topic here, as that my Liteon L100 gps runs on Window CE, has MP3 and Photo
viewing. It had a 1 GB data card. On the card are; maps and POI of North
America and system data.
When I sync to upload MP3 file, I get an unresolved issue and seemly the
data card is full. I manage to get a folder with the name of the MP3 file on
the card, but I cannot access the file.
If all I need is a 2GB card I will get one. I think that there is a
formatting issue also for a new card.
P.S. I have owned three generation of Garmin and still use a Quest 1 on my
bicycle. I am converting my LPs to MP3 and WAV files stored on my computer.

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