The 120 mb reading is right. It's a bit strange the way companies rate the size of their cards. They measure a megabyte as 1000 kilobytes, when it is actually 1024. This is why there is a size discrepency (sp?) The axim is right with the 128 meg card though.
As for your 64 meg card, it should be showing something more like 60 or so megs. You may want to try reformatting it using storage tools or another application.
Edit: Damn I'm a slow typer, beaten to it again

EEG is also right about the formating, it takes up about 1-2 megs on the card I believe.