Suggestions on a device that could play AVI and FLAC?

[Extraterrestrial]

I don't know about SD card reader chipsets, but most likely it will not read a 4gb.
I have noticed that most devices say up to 2gb or up to 4gb.
Besides I believe there are no 4gb SD cards, only SDHC.
You may want to open the device and check the ID on the chip, Samsung's and Hynix's ID sheets are all over the internet (to see the real capacity of the chip)
In some rare cases people found bigger chips formatted at a lower size.

I'm not a hardware expert, but I can tell you what is written on the chipset which is (Kingston SDC4/4GB) and it reads 3.75 GB on my computer

[desodorante]

I'm not a hardware expert, but I can tell you what is written on the chipset which is (Kingston SDC4/4GB) and it reads 3.75 GB on my computer

Actually I meant inside the player. The memory chips are from Samsung 75% of the time, Hynix 20% and generic 5%.
They have an ID which you can translate to a size in Gigabytes.
Something like you can see here S1mp3.org - Firmware replacement for s1 mp3 player - Hardware specs (Check item [H]) , below you have a quick chart to decode what it means
Anyway it was just an idea, check if your SDC card works, I am not sure how much memory you need for you FLAC discography and films. Good luck!