I have a 4GB SD memory card (not is HC) and the front of the card shows as normal SD CARD. The shop told me this card is for old units.
Now, in the properties of the card, I'm seeing the information display as FAT32. I think this card is HC because that all SD card (not HC) only can be FAT 16bits. I'm wrong?

Anything over 2GB should be FAT32 as FAT16 has a maximum file size of 2GB, I use FAT32 on every card i have regardless of size.

Sorry for my doubt, my GPS unit (Becker 7934) can't read FAT32, and doesn't have flash rom or another way to upgrade to support FAT32. How can I to have sure if this SD card (not HC) is compatible before buy? If came with FAT32 how is possible to be a normal SD (not HC)?

If there is not going to be any files larger than 2GB then format it as FAT16 (Sometimes just called FAT)

Some SD card reader drivers have lower limits on card size, particularly if they are not compliant with official specifications, I had an ancient USB card reader that won't read SD cards larger than 512MB