Some notes.

"buy a new SD card"
The "new" SD cards are generally Class 10 high speed cards and large capacity. Make sure you get a Class 4 card, the high speed cards don't work well.

As for Formatting the card, don't use your computer to format it, go to SDCard.org and download SDFormatter, use that to format the cards. https://www.sdcard.org/downloads/formatter_4/