Hi you will lose all data if you format but if it's a new card, yes format. If you don't mind losing data then yes format. Just so you know, right now Amazon has some really good prices on sd cards if your looking for a bigger card. I just bought a 64gig SanDisk class 10 micro sd for around 50.00 which is a pretty good deal. They have 32 gig for about 30 bucks right now too .
The prices get even lower for the smaller ones. I learned something however on the 64 at first device will recognize it as a damaged card until you format it in your device. You can do it from recovery by pulling battery, putting battery back in, press power and volume down and get in recovery that way. Other wise it will say damaged card, sd is needed to get into recovery if you try and get there straight from the device. But if you pull battery you can get to recovery that way then in 4ext press format sd card. Then the 64 will register and you can use it without Any problem. Hope this helps you and best wishes.
Sent from HTC sensation, soff, 3.33 firmware, viper Rom, sense 4.1,kernel- pyd X stable 3.1 , Mugen 3800 mah battery. Please press thanks if I helped in anyway.
