Welcome to DK.
It should be a 2GB SD not SDHC card formatted FAT32 in Windows.
There are more than 2 files in LetterBomb.zip. Format the SD card FAT32 and extract all files\folders from the zip into the SD card.
That picture looks like your using an SDHC card thats why it can't find the files. An SDHC card will work perfectly after its been softmodded.