Computer won't recognise 4GB cards

railfan wrote:
My computer is several years old and works fine so I don't want to
replace it yet. It has a multi card reader built in, and I've always
downloaded my digital images this way. It won't recognise cards
larger than 2GB, and I understand that such cards use the FAT 32
format, smaller ones use FAT 16 or ?

Possibly. With the de-facto standard 512B sector size FAT16 cannot
address more than 2GB. While FAT16 can be formatted using larger sector
sizes this is quite uncommon (some old magneto-optical media come to
mind). So yes, for larger partitions typically FAT32 is used.
But there is nothing stopping anyone from using FAT32 for smaller
partitions, either.

I tried two different 4GB SD
cards and nothing at all happens when they are inserted into the slot.

This is your problem. The original SD 1.x standard specified the maximum
size of an SD card as 2GB. Therefore until very recently there was no
legitimate 4GB SD card. You either got
- an SDHC card, which cannot be read by SD-only readers
- a proprietary extension of SD created by some manufacturers, which may
or may not work on a given reader
- or recently the SD consortium changed the spec for SD to allow block
sizes larger than 512GB but of course your older card reader won't know
about that and won't be able to handle those cards.

I mentioned this to a fellow recently who said he was a computer tech,
suggested I get a separate card reader, plug it into the USB slot and
it should download 4GB (or larger) cards. I can't see how a card
reader could do this, but there possibly could be something to it.

A newer card reader should(!) be SDHC or SD 2.0 compliant and understand
the new format for SDHC and/or SD with a block size over 512B.

Perhaps there are electronics in a reader that would process the
images?

No. A card reader is a dumb device, that simply presents a memory card
as an external drive to the computer. It doesn't know anything about the
data that is stored on a card.

jue