"battery is dry or first in" is an error message telling you the coin cell battery on the board is out of power. That battery is used to power the SRAM chip which holds the savegame of the last played title.
I assume this is an older white EZFlash IV model?
Either way, the first thing you need to do, is replace that battery by desoldering it and soldering in a new one (tabbed batteries can be found on ebay for a few bucks)
Second, it looks like your sd card has suffered corruption - could be an interrupted write or it could just have died of old age. I recommend taking it out, putting it in a computer and run a disk check on it to solve any errors and copy everything from the card to your PC. Once everything has copied over, do a fresh format on the card and copy everything back onto it or maybe even use a different SD card.
Third, you might want to look into upgrading your card to an up to date kernel (2.05) - depending on the sd card you're currently using, this might require you to get a new SD card though as the newer kernels have become incompatible with non-sdhc cards.
Also, this might require you to get new copies of your ROMs. If you're on an older kernel, your roms might have been patched using the EZFlash PC Client - newer kernels require the ROMs to be completely unpatched/clean (the card will handle this at runtime!)
Make sure you read up on what's changed and what you need to be aware of before upgrading.